<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:4013baa2-13f0-4e3d-94b1-0bc00eaf0d6e,g:2196a36b-1681-412d-9fc3-637d7a808d41-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.cloudflare.com/role/Cover" xlink:type="simple" xlink:href="cloud-20220331.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/Cover" xlink:type="extended" id="i536636d491564a19b826e60892bafc6e_Cover">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_14311cb6-9a3b-4362-a9dc-f4a93875a170" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_DocumentType_14311cb6-9a3b-4362-a9dc-f4a93875a170" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_c9716b15-eaf4-4bee-84a6-9a8466252114" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_DocumentQuarterlyReport_c9716b15-eaf4-4bee-84a6-9a8466252114" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_c4b875eb-b794-4ccd-85db-2c83769d1f9b" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_DocumentPeriodEndDate_c4b875eb-b794-4ccd-85db-2c83769d1f9b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_2c68d9ed-424a-4105-bff6-59526179a22e" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_DocumentTransitionReport_2c68d9ed-424a-4105-bff6-59526179a22e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_11a8ab42-7cc1-4e05-b5d3-01a977024217" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityFileNumber_11a8ab42-7cc1-4e05-b5d3-01a977024217" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_cdedefaf-febf-44ef-bebe-0007383f5746" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityRegistrantName_cdedefaf-febf-44ef-bebe-0007383f5746" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_50724cfa-34ba-4889-94e0-dba8a01be238" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityIncorporationStateCountryCode_50724cfa-34ba-4889-94e0-dba8a01be238" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_e439d950-1950-4b5b-9a4d-65490e1ce02a" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityTaxIdentificationNumber_e439d950-1950-4b5b-9a4d-65490e1ce02a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_7c3a7c9f-d0c5-4216-bd6f-e1206a9849cc" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityAddressAddressLine1_7c3a7c9f-d0c5-4216-bd6f-e1206a9849cc" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_e281b467-23c9-495f-8bef-68e4864af61a" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityAddressCityOrTown_e281b467-23c9-495f-8bef-68e4864af61a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_a3c83695-b0a4-4494-9e21-74808f9f6a27" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityAddressStateOrProvince_a3c83695-b0a4-4494-9e21-74808f9f6a27" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_3a8851c5-cfa3-4446-a24d-6fa5ea68851f" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityAddressPostalZipCode_3a8851c5-cfa3-4446-a24d-6fa5ea68851f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_db0ad5dd-43ea-4f00-b89c-69be0097aa31" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_CityAreaCode_db0ad5dd-43ea-4f00-b89c-69be0097aa31" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_733eb53e-689d-43c6-ae25-722271339350" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_LocalPhoneNumber_733eb53e-689d-43c6-ae25-722271339350" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_aab635af-df34-450b-9ef8-04512226fdab" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_Security12bTitle_aab635af-df34-450b-9ef8-04512226fdab" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_1686e194-9f98-444d-b7ae-77785b5c3b8a" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_TradingSymbol_1686e194-9f98-444d-b7ae-77785b5c3b8a" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_0556c25a-58ce-469b-9e03-75fb99f01c33" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_SecurityExchangeName_0556c25a-58ce-469b-9e03-75fb99f01c33" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_3e6affdd-2332-4845-accf-5470afc3ca44" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityCurrentReportingStatus_3e6affdd-2332-4845-accf-5470afc3ca44" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_21b9d4b9-b444-4287-8e70-06e4da90f933" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityInteractiveDataCurrent_21b9d4b9-b444-4287-8e70-06e4da90f933" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_7b1a42a1-f4a7-4f96-8bf9-0aecf1afc088" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityFilerCategory_7b1a42a1-f4a7-4f96-8bf9-0aecf1afc088" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_23655fb7-c9a9-440b-876b-7fde1047bc7c" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntitySmallBusiness_23655fb7-c9a9-440b-876b-7fde1047bc7c" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_da417edb-9908-4fbe-b0c0-4cf6278ce7c4" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityEmergingGrowthCompany_da417edb-9908-4fbe-b0c0-4cf6278ce7c4" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_250f8e3d-e6c0-4363-b017-0ca37d778464" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityShellCompany_250f8e3d-e6c0-4363-b017-0ca37d778464" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_fa643380-082e-4fca-8007-209fdc0f9ebe" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_fa643380-082e-4fca-8007-209fdc0f9ebe" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_75cbc633-d337-4208-a6c3-ad462ab73e3c" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_AmendmentFlag_75cbc633-d337-4208-a6c3-ad462ab73e3c" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_e37cbaa6-b4c6-4b16-8a49-214586fa443b" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_EntityCentralIndexKey_e37cbaa6-b4c6-4b16-8a49-214586fa443b" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_3454bbd4-dba0-4c0c-a664-c565912e505f" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_DocumentFiscalPeriodFocus_3454bbd4-dba0-4c0c-a664-c565912e505f" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_f40d65dc-2448-44a2-a530-c4170058c726" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_DocumentFiscalYearFocus_f40d65dc-2448-44a2-a530-c4170058c726" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_ca050779-77f7-49ad-aa2d-8cc1ca7fc7c8" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_CurrentFiscalYearEndDate_ca050779-77f7-49ad-aa2d-8cc1ca7fc7c8" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_241910bc-fbde-446d-9eba-511180e8d707" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_339b9f54-1dcf-4ad7-8603-f615d122c604" xlink:to="loc_dei_DocumentInformationTable_241910bc-fbde-446d-9eba-511180e8d707" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_cfeea8e7-1163-409b-af44-99f5daf6180e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_241910bc-fbde-446d-9eba-511180e8d707" xlink:to="loc_us-gaap_StatementClassOfStockAxis_cfeea8e7-1163-409b-af44-99f5daf6180e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_cfeea8e7-1163-409b-af44-99f5daf6180e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_cfeea8e7-1163-409b-af44-99f5daf6180e" xlink:to="loc_us-gaap_ClassOfStockDomain_cfeea8e7-1163-409b-af44-99f5daf6180e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_62dade37-5618-4871-9366-f25a3fce3330" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_cfeea8e7-1163-409b-af44-99f5daf6180e" xlink:to="loc_us-gaap_ClassOfStockDomain_62dade37-5618-4871-9366-f25a3fce3330" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_e3b82203-47c4-4973-895d-4b58d0a00484" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_62dade37-5618-4871-9366-f25a3fce3330" xlink:to="loc_us-gaap_CommonClassAMember_e3b82203-47c4-4973-895d-4b58d0a00484" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_2d112ab6-f349-4622-830e-4ae3e7cdbe2b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_62dade37-5618-4871-9366-f25a3fce3330" xlink:to="loc_us-gaap_CommonClassBMember_2d112ab6-f349-4622-830e-4ae3e7cdbe2b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="cloud-20220331.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETS"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="extended" id="i0e3494b9e1ff47089cce591cf7954576_CONDENSEDCONSOLIDATEDBALANCESHEETS">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_01438861-f6fa-47d8-8cf6-d2c37731a82f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_2ecdb471-7be2-4db8-91d2-1cefaab18bbd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_01438861-f6fa-47d8-8cf6-d2c37731a82f" xlink:to="loc_us-gaap_AssetsAbstract_2ecdb471-7be2-4db8-91d2-1cefaab18bbd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_64739f61-a381-4f0c-aadd-39e1cd6bda3c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2ecdb471-7be2-4db8-91d2-1cefaab18bbd" xlink:to="loc_us-gaap_AssetsCurrentAbstract_64739f61-a381-4f0c-aadd-39e1cd6bda3c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_d38df080-0e15-460e-b9cc-f1dc06d06fc6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_64739f61-a381-4f0c-aadd-39e1cd6bda3c" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_d38df080-0e15-460e-b9cc-f1dc06d06fc6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_6d49acac-42f6-4048-8ef4-93f7531172a7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_64739f61-a381-4f0c-aadd-39e1cd6bda3c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_6d49acac-42f6-4048-8ef4-93f7531172a7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_5e03a3a8-6217-4e0d-8df9-32995fe61cc0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_64739f61-a381-4f0c-aadd-39e1cd6bda3c" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_5e03a3a8-6217-4e0d-8df9-32995fe61cc0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetCurrent_cced9edd-01be-4cd4-95d5-7202bd258a0f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerAssetNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_64739f61-a381-4f0c-aadd-39e1cd6bda3c" xlink:to="loc_us-gaap_ContractWithCustomerAssetNetCurrent_cced9edd-01be-4cd4-95d5-7202bd258a0f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashCurrent_9839ceb7-d19e-4e93-9375-a2a0a7429a85" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedCashCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_64739f61-a381-4f0c-aadd-39e1cd6bda3c" xlink:to="loc_us-gaap_RestrictedCashCurrent_9839ceb7-d19e-4e93-9375-a2a0a7429a85" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_a0776bbb-47f1-479a-b7f4-f25ae4da6c65" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_64739f61-a381-4f0c-aadd-39e1cd6bda3c" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_a0776bbb-47f1-479a-b7f4-f25ae4da6c65" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_cbc955e3-fadd-4d43-8e20-fd58531e5744" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_64739f61-a381-4f0c-aadd-39e1cd6bda3c" xlink:to="loc_us-gaap_AssetsCurrent_cbc955e3-fadd-4d43-8e20-fd58531e5744" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_7f9fec10-eb7f-4cf0-b259-048517d3b657" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2ecdb471-7be2-4db8-91d2-1cefaab18bbd" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_7f9fec10-eb7f-4cf0-b259-048517d3b657" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_c65b2af0-7e0f-4284-b6cf-ab2b2586294c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2ecdb471-7be2-4db8-91d2-1cefaab18bbd" xlink:to="loc_us-gaap_Goodwill_c65b2af0-7e0f-4284-b6cf-ab2b2586294c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_3f26548e-21a3-4706-9d74-0bff3a14b0f5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2ecdb471-7be2-4db8-91d2-1cefaab18bbd" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_3f26548e-21a3-4706-9d74-0bff3a14b0f5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_7251fb83-a230-4ea6-a7d1-bfdc69c8149a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2ecdb471-7be2-4db8-91d2-1cefaab18bbd" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_7251fb83-a230-4ea6-a7d1-bfdc69c8149a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostNetNoncurrent_8f94a813-a795-4030-89f0-1f01dd456a11" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CapitalizedContractCostNetNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2ecdb471-7be2-4db8-91d2-1cefaab18bbd" xlink:to="loc_us-gaap_CapitalizedContractCostNetNoncurrent_8f94a813-a795-4030-89f0-1f01dd456a11" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashNoncurrent_f0aaf158-0128-45e0-83a3-2fa0df98b682" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedCashNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2ecdb471-7be2-4db8-91d2-1cefaab18bbd" xlink:to="loc_us-gaap_RestrictedCashNoncurrent_f0aaf158-0128-45e0-83a3-2fa0df98b682" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_1d584048-bb1d-462b-b721-c79f73b96807" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2ecdb471-7be2-4db8-91d2-1cefaab18bbd" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_1d584048-bb1d-462b-b721-c79f73b96807" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_ef76a307-02ca-4ad2-94f2-2edd68d5b57c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_2ecdb471-7be2-4db8-91d2-1cefaab18bbd" xlink:to="loc_us-gaap_Assets_ef76a307-02ca-4ad2-94f2-2edd68d5b57c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_229535bf-02ca-4b1c-a28a-76167f8fb07a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_01438861-f6fa-47d8-8cf6-d2c37731a82f" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_229535bf-02ca-4b1c-a28a-76167f8fb07a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_6420a5aa-d87f-4199-8eb9-7c0a6b030f3c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_229535bf-02ca-4b1c-a28a-76167f8fb07a" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_6420a5aa-d87f-4199-8eb9-7c0a6b030f3c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_ce44bb9d-756b-4389-8415-c9fb6dfc5980" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_6420a5aa-d87f-4199-8eb9-7c0a6b030f3c" xlink:to="loc_us-gaap_AccountsPayableCurrent_ce44bb9d-756b-4389-8415-c9fb6dfc5980" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_AccruedLiabilitiesAndOtherLiabilitiesCurrent_838c655f-839b-4c02-9ffa-d72f2640085b" xlink:href="cloud-20220331.xsd#cloud_AccruedLiabilitiesAndOtherLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_6420a5aa-d87f-4199-8eb9-7c0a6b030f3c" xlink:to="loc_cloud_AccruedLiabilitiesAndOtherLiabilitiesCurrent_838c655f-839b-4c02-9ffa-d72f2640085b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_a71be6d2-cb3e-41dd-a87c-e3aeec2d6e31" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_6420a5aa-d87f-4199-8eb9-7c0a6b030f3c" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_a71be6d2-cb3e-41dd-a87c-e3aeec2d6e31" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_e0280d00-5feb-4261-9d9b-372dc39e3f1b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_6420a5aa-d87f-4199-8eb9-7c0a6b030f3c" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_e0280d00-5feb-4261-9d9b-372dc39e3f1b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationShareBasedArrangementsLiabilityCurrent_c128076c-83b2-4581-8271-1bb477e0cfe2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationShareBasedArrangementsLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_6420a5aa-d87f-4199-8eb9-7c0a6b030f3c" xlink:to="loc_us-gaap_DeferredCompensationShareBasedArrangementsLiabilityCurrent_c128076c-83b2-4581-8271-1bb477e0cfe2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_8e353406-6159-4c01-bddc-97f6bc2705dd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_6420a5aa-d87f-4199-8eb9-7c0a6b030f3c" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_8e353406-6159-4c01-bddc-97f6bc2705dd" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtCurrent_186b2933-46c9-4a86-8b70-6bbb209dfe8c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_6420a5aa-d87f-4199-8eb9-7c0a6b030f3c" xlink:to="loc_us-gaap_ConvertibleDebtCurrent_186b2933-46c9-4a86-8b70-6bbb209dfe8c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_dce26404-1787-453b-9b3d-218e17bf19f0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_6420a5aa-d87f-4199-8eb9-7c0a6b030f3c" xlink:to="loc_us-gaap_LiabilitiesCurrent_dce26404-1787-453b-9b3d-218e17bf19f0" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtNoncurrent_4521390d-f501-4216-b78b-fe63132fa75a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_229535bf-02ca-4b1c-a28a-76167f8fb07a" xlink:to="loc_us-gaap_ConvertibleDebtNoncurrent_4521390d-f501-4216-b78b-fe63132fa75a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_fd1ccaea-1cf5-4589-988a-3c45f6d43d5c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_229535bf-02ca-4b1c-a28a-76167f8fb07a" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_fd1ccaea-1cf5-4589-988a-3c45f6d43d5c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_b0c1ccde-8a23-4522-8d7d-b36fd454f2c2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_229535bf-02ca-4b1c-a28a-76167f8fb07a" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_b0c1ccde-8a23-4522-8d7d-b36fd454f2c2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_f639f6a2-7475-4f02-a4b1-461a6c61aee9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_229535bf-02ca-4b1c-a28a-76167f8fb07a" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_f639f6a2-7475-4f02-a4b1-461a6c61aee9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_44d8be45-c6ee-4acf-96fd-f301754c3e9d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_229535bf-02ca-4b1c-a28a-76167f8fb07a" xlink:to="loc_us-gaap_Liabilities_44d8be45-c6ee-4acf-96fd-f301754c3e9d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_51c78037-de4f-4f05-ab18-2af713427232" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_229535bf-02ca-4b1c-a28a-76167f8fb07a" xlink:to="loc_us-gaap_CommitmentsAndContingencies_51c78037-de4f-4f05-ab18-2af713427232" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_ceeecbb7-2cba-4d6a-b21a-00d9cf8b1cce" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_229535bf-02ca-4b1c-a28a-76167f8fb07a" xlink:to="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_ceeecbb7-2cba-4d6a-b21a-00d9cf8b1cce" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityAbstract_412a3e92-bb26-47e5-8943-06a95f0c938e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_229535bf-02ca-4b1c-a28a-76167f8fb07a" xlink:to="loc_us-gaap_StockholdersEquityAbstract_412a3e92-bb26-47e5-8943-06a95f0c938e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_6d4fdeee-3e81-4b36-bad9-bc0e8e0c43b0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_412a3e92-bb26-47e5-8943-06a95f0c938e" xlink:to="loc_us-gaap_CommonStockValue_6d4fdeee-3e81-4b36-bad9-bc0e8e0c43b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_cff4c771-6ef3-479b-b0fd-f4c1f8a427f4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_412a3e92-bb26-47e5-8943-06a95f0c938e" xlink:to="loc_us-gaap_AdditionalPaidInCapital_cff4c771-6ef3-479b-b0fd-f4c1f8a427f4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_57b03448-25ff-4a6d-8586-a76d48d3501a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_412a3e92-bb26-47e5-8943-06a95f0c938e" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_57b03448-25ff-4a6d-8586-a76d48d3501a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_17ecc3f4-23f0-423b-aaf4-33884428d8a1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_412a3e92-bb26-47e5-8943-06a95f0c938e" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_17ecc3f4-23f0-423b-aaf4-33884428d8a1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_0dba3093-5402-477a-9a09-74fe3680d5c1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_412a3e92-bb26-47e5-8943-06a95f0c938e" xlink:to="loc_us-gaap_StockholdersEquity_0dba3093-5402-477a-9a09-74fe3680d5c1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_2bcd022b-41bb-4267-a432-6610cda4a79b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_229535bf-02ca-4b1c-a28a-76167f8fb07a" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_2bcd022b-41bb-4267-a432-6610cda4a79b" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_f9389c48-7ffb-4ee6-8542-ceb442414311" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_01438861-f6fa-47d8-8cf6-d2c37731a82f" xlink:to="loc_us-gaap_StatementTable_f9389c48-7ffb-4ee6-8542-ceb442414311" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_afdb1507-e4b0-463d-a243-00456d4aa964" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_f9389c48-7ffb-4ee6-8542-ceb442414311" xlink:to="loc_us-gaap_StatementClassOfStockAxis_afdb1507-e4b0-463d-a243-00456d4aa964" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_afdb1507-e4b0-463d-a243-00456d4aa964_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_afdb1507-e4b0-463d-a243-00456d4aa964" xlink:to="loc_us-gaap_ClassOfStockDomain_afdb1507-e4b0-463d-a243-00456d4aa964_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_4d5827e8-3990-4a5a-90b5-283bf4c653f6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_afdb1507-e4b0-463d-a243-00456d4aa964" xlink:to="loc_us-gaap_ClassOfStockDomain_4d5827e8-3990-4a5a-90b5-283bf4c653f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_815ac190-873f-444f-bacc-98357fd2276d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_4d5827e8-3990-4a5a-90b5-283bf4c653f6" xlink:to="loc_us-gaap_CommonClassAMember_815ac190-873f-444f-bacc-98357fd2276d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_42602741-9552-47b5-abf1-4959029a514b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_4d5827e8-3990-4a5a-90b5-283bf4c653f6" xlink:to="loc_us-gaap_CommonClassBMember_42602741-9552-47b5-abf1-4959029a514b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="simple" xlink:href="cloud-20220331.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="extended" id="id437b66a99154bc6b76270fcdf9aca58_CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_d3e13359-e1a6-4f29-806e-b7550f1c672a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityAbstract_2d86c9f2-ccb1-4b2b-bae9-27e3ede58ee0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d3e13359-e1a6-4f29-806e-b7550f1c672a" xlink:to="loc_us-gaap_StockholdersEquityAbstract_2d86c9f2-ccb1-4b2b-bae9-27e3ede58ee0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_15b530b5-8f76-49e9-a1d7-669a03b5959d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_2d86c9f2-ccb1-4b2b-bae9-27e3ede58ee0" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_15b530b5-8f76-49e9-a1d7-669a03b5959d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_9acf9159-06a1-43e9-adca-4fe6ae893980" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_2d86c9f2-ccb1-4b2b-bae9-27e3ede58ee0" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_9acf9159-06a1-43e9-adca-4fe6ae893980" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_f964a2b5-aff0-4ccb-96fb-fec8de49791f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_2d86c9f2-ccb1-4b2b-bae9-27e3ede58ee0" xlink:to="loc_us-gaap_CommonStockSharesIssued_f964a2b5-aff0-4ccb-96fb-fec8de49791f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_de23195d-76eb-42b2-a992-5e918efe9b5a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_2d86c9f2-ccb1-4b2b-bae9-27e3ede58ee0" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_de23195d-76eb-42b2-a992-5e918efe9b5a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_3c6cc6c8-ca09-4300-911d-e992b0889c95" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_d3e13359-e1a6-4f29-806e-b7550f1c672a" xlink:to="loc_us-gaap_StatementTable_3c6cc6c8-ca09-4300-911d-e992b0889c95" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_2f282c74-d326-4d85-9262-04b3cf893ee0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_3c6cc6c8-ca09-4300-911d-e992b0889c95" xlink:to="loc_us-gaap_StatementClassOfStockAxis_2f282c74-d326-4d85-9262-04b3cf893ee0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_2f282c74-d326-4d85-9262-04b3cf893ee0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_2f282c74-d326-4d85-9262-04b3cf893ee0" xlink:to="loc_us-gaap_ClassOfStockDomain_2f282c74-d326-4d85-9262-04b3cf893ee0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_24fae687-0031-417e-8ad4-37ac59429828" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_2f282c74-d326-4d85-9262-04b3cf893ee0" xlink:to="loc_us-gaap_ClassOfStockDomain_24fae687-0031-417e-8ad4-37ac59429828" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_a32b9622-b8a2-461a-9270-75075ca84b0b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_24fae687-0031-417e-8ad4-37ac59429828" xlink:to="loc_us-gaap_CommonClassAMember_a32b9622-b8a2-461a-9270-75075ca84b0b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_90d4568f-157c-406b-9da7-bc5bff332541" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_24fae687-0031-417e-8ad4-37ac59429828" xlink:to="loc_us-gaap_CommonClassBMember_90d4568f-157c-406b-9da7-bc5bff332541" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="simple" xlink:href="cloud-20220331.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="extended" id="ib6ead30e70474a9b8f03ee3d94af3a3e_CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_1d4be3ea-52ec-49bd-bb20-2912d80178fa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountingStandardsUpdateExtensibleList_0e5f4f09-6c3e-4e97-8077-3ce7ef6ae714" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountingStandardsUpdateExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1d4be3ea-52ec-49bd-bb20-2912d80178fa" xlink:to="loc_us-gaap_AccountingStandardsUpdateExtensibleList_0e5f4f09-6c3e-4e97-8077-3ce7ef6ae714" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1d4be3ea-52ec-49bd-bb20-2912d80178fa" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_11d830be-d010-42e7-9e29-d6a2dffde0ae" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_11d830be-d010-42e7-9e29-d6a2dffde0ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_90a77312-ca11-44b7-8ade-b2ad9dd0e35f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_StockholdersEquity_90a77312-ca11-44b7-8ade-b2ad9dd0e35f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_a509d5ee-28d8-4387-a5f6-880bc8f1b67e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_a509d5ee-28d8-4387-a5f6-880bc8f1b67e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_4dd9f838-d065-4903-8b18-6d7a44af79c7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_4dd9f838-d065-4903-8b18-6d7a44af79c7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_IssuanceOfUnvestedRestrictedStockInConnectionWithAcquisitionShares_72eb1aa7-88e9-4825-b797-ceb56a60d9ac" xlink:href="cloud-20220331.xsd#cloud_IssuanceOfUnvestedRestrictedStockInConnectionWithAcquisitionShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_cloud_IssuanceOfUnvestedRestrictedStockInConnectionWithAcquisitionShares_72eb1aa7-88e9-4825-b797-ceb56a60d9ac" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_2d85d06c-6948-463f-8c63-27598ec601ba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_2d85d06c-6948-463f-8c63-27598ec601ba" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_b8de083b-a308-49bf-82f1-8a9c097931ff" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_b8de083b-a308-49bf-82f1-8a9c097931ff" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_6aa5b13c-e45e-4c1a-8499-298ebaca8d84" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_6aa5b13c-e45e-4c1a-8499-298ebaca8d84" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsEarlyExercisesInPeriod_d2e93431-001d-4868-bc30-ce9ba9a3af37" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsEarlyExercisesInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsEarlyExercisesInPeriod_d2e93431-001d-4868-bc30-ce9ba9a3af37" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_APICShareBasedPaymentArrangementIncreaseForStockOptionsEarlyExercised_4c80bbb5-1712-44b1-927b-86b6524fe8bb" xlink:href="cloud-20220331.xsd#cloud_APICShareBasedPaymentArrangementIncreaseForStockOptionsEarlyExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_cloud_APICShareBasedPaymentArrangementIncreaseForStockOptionsEarlyExercised_4c80bbb5-1712-44b1-927b-86b6524fe8bb" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_afbcd035-fe71-4d02-9eb1-d16446c4a2be" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_afbcd035-fe71-4d02-9eb1-d16446c4a2be" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross_99d64ee0-0c5f-4872-bb63-75d9f7f41d71" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross_99d64ee0-0c5f-4872-bb63-75d9f7f41d71" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_c9578ccb-fcdc-426b-84be-0b7f974575cc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_c9578ccb-fcdc-426b-84be-0b7f974575cc" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_d07b8730-0a17-451f-a7ee-54bb0e653709" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_d07b8730-0a17-451f-a7ee-54bb0e653709" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_StockIssuedDuringPeriodSharesConversionOfShares_876f0169-3547-4d4a-a150-d9095a967ea8" xlink:href="cloud-20220331.xsd#cloud_StockIssuedDuringPeriodSharesConversionOfShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_cloud_StockIssuedDuringPeriodSharesConversionOfShares_876f0169-3547-4d4a-a150-d9095a967ea8" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_StockIssuedDuringPeriodValueConversionOfShares_2d51169b-3c72-4a5a-8c30-73642e2630dc" xlink:href="cloud-20220331.xsd#cloud_StockIssuedDuringPeriodValueConversionOfShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_cloud_StockIssuedDuringPeriodValueConversionOfShares_2d51169b-3c72-4a5a-8c30-73642e2630dc" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_8a13a07c-13a0-4bea-80cb-3e2c733bb24d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_8a13a07c-13a0-4bea-80cb-3e2c733bb24d" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalEquityComponentOfConvertibleDebtSubsequentAdjustments_7019f90e-d7ee-4c12-90c7-3b9ad0c09a97" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalEquityComponentOfConvertibleDebtSubsequentAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalEquityComponentOfConvertibleDebtSubsequentAdjustments_7019f90e-d7ee-4c12-90c7-3b9ad0c09a97" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_6738e283-b625-46ae-8077-7094e11874c0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_6738e283-b625-46ae-8077-7094e11874c0" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_77a0dcfd-7a2f-4953-aa1d-de160d775d3c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_NetIncomeLoss_77a0dcfd-7a2f-4953-aa1d-de160d775d3c" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_b2c81455-d50a-4277-b82e-be6611e1e400" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0174d8a0-de41-471c-9244-cf05da82ca2a" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_b2c81455-d50a-4277-b82e-be6611e1e400" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_8a3fdfc0-f83d-4bae-8edd-7be4cddb0dc5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_d0ea057f-062c-4363-a2de-82f4ef688611" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_d8f20570-870a-4950-b0a7-f9508b9ec20b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1d4be3ea-52ec-49bd-bb20-2912d80178fa" xlink:to="loc_us-gaap_StatementTable_d8f20570-870a-4950-b0a7-f9508b9ec20b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_5eae3fe7-622c-4f9d-aed9-2f15e59b4a78" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_d8f20570-870a-4950-b0a7-f9508b9ec20b" xlink:to="loc_us-gaap_StatementClassOfStockAxis_5eae3fe7-622c-4f9d-aed9-2f15e59b4a78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_5eae3fe7-622c-4f9d-aed9-2f15e59b4a78_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_5eae3fe7-622c-4f9d-aed9-2f15e59b4a78" xlink:to="loc_us-gaap_ClassOfStockDomain_5eae3fe7-622c-4f9d-aed9-2f15e59b4a78_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_a4da82c3-1d0a-4728-b156-17ba6ffb77fd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_5eae3fe7-622c-4f9d-aed9-2f15e59b4a78" xlink:to="loc_us-gaap_ClassOfStockDomain_a4da82c3-1d0a-4728-b156-17ba6ffb77fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_bc95e362-e849-44aa-bee6-da9b24c0875e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_a4da82c3-1d0a-4728-b156-17ba6ffb77fd" xlink:to="loc_us-gaap_CommonClassAMember_bc95e362-e849-44aa-bee6-da9b24c0875e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_4c60935a-9195-4e25-87ba-cda94c6535dd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_a4da82c3-1d0a-4728-b156-17ba6ffb77fd" xlink:to="loc_us-gaap_CommonClassBMember_4c60935a-9195-4e25-87ba-cda94c6535dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_a7fd13f7-995a-4135-83ea-cebc57715fbf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_d8f20570-870a-4950-b0a7-f9508b9ec20b" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_a7fd13f7-995a-4135-83ea-cebc57715fbf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_a7fd13f7-995a-4135-83ea-cebc57715fbf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_a7fd13f7-995a-4135-83ea-cebc57715fbf" xlink:to="loc_us-gaap_EquityComponentDomain_a7fd13f7-995a-4135-83ea-cebc57715fbf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_fcbeab4d-2b74-4fef-a114-a0535a3f18f9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_a7fd13f7-995a-4135-83ea-cebc57715fbf" xlink:to="loc_us-gaap_EquityComponentDomain_fcbeab4d-2b74-4fef-a114-a0535a3f18f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_982f2c68-4e27-4d4e-bb41-e4e93c5da064" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_fcbeab4d-2b74-4fef-a114-a0535a3f18f9" xlink:to="loc_us-gaap_CommonStockMember_982f2c68-4e27-4d4e-bb41-e4e93c5da064" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_420c373a-0138-44fc-b3c0-af41a97fd044" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_fcbeab4d-2b74-4fef-a114-a0535a3f18f9" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_420c373a-0138-44fc-b3c0-af41a97fd044" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_6fdfb4db-0c86-4b00-ad74-1aa6cb12ec5c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_fcbeab4d-2b74-4fef-a114-a0535a3f18f9" xlink:to="loc_us-gaap_RetainedEarningsMember_6fdfb4db-0c86-4b00-ad74-1aa6cb12ec5c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_46f29bb6-4509-45f9-88e1-8fa239428771" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_fcbeab4d-2b74-4fef-a114-a0535a3f18f9" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_46f29bb6-4509-45f9-88e1-8fa239428771" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_ac74543f-81c1-4969-9f8f-af8470dc4e12" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_d8f20570-870a-4950-b0a7-f9508b9ec20b" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_ac74543f-81c1-4969-9f8f-af8470dc4e12" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_ac74543f-81c1-4969-9f8f-af8470dc4e12_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_ac74543f-81c1-4969-9f8f-af8470dc4e12" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_ac74543f-81c1-4969-9f8f-af8470dc4e12_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_00cbe233-3e5a-41c0-840a-dcca8c2c269c" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_ac74543f-81c1-4969-9f8f-af8470dc4e12" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_00cbe233-3e5a-41c0-840a-dcca8c2c269c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_cf32ae40-cef5-446d-bbc7-4767ece51c09" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_00cbe233-3e5a-41c0-840a-dcca8c2c269c" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_cf32ae40-cef5-446d-bbc7-4767ece51c09" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/SummaryofSignificantAccountingPoliciesDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#SummaryofSignificantAccountingPoliciesDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/SummaryofSignificantAccountingPoliciesDetails" xlink:type="extended" id="i4a9b1528c79e4460989bfe415381c624_SummaryofSignificantAccountingPoliciesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_63c8e0af-d09d-453b-9569-4cacda5ca406" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_2f29de16-9377-4511-b4f5-50cbcfedc1d8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_63c8e0af-d09d-453b-9569-4cacda5ca406" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_2f29de16-9377-4511-b4f5-50cbcfedc1d8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebt_4803f5d4-0aa8-40e3-9a81-b70dbbe1b206" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_63c8e0af-d09d-453b-9569-4cacda5ca406" xlink:to="loc_us-gaap_ConvertibleDebt_4803f5d4-0aa8-40e3-9a81-b70dbbe1b206" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtCurrent_c6f62836-4957-4e4d-a53e-ff1fb2816630" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_63c8e0af-d09d-453b-9569-4cacda5ca406" xlink:to="loc_us-gaap_ConvertibleDebtCurrent_c6f62836-4957-4e4d-a53e-ff1fb2816630" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_fba67eb9-8e0a-438b-8a56-4d1beec97a3f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_63c8e0af-d09d-453b-9569-4cacda5ca406" xlink:to="loc_us-gaap_AdditionalPaidInCapital_fba67eb9-8e0a-438b-8a56-4d1beec97a3f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_3ef6b2bd-297f-400d-a784-f22f9179c8b7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_63c8e0af-d09d-453b-9569-4cacda5ca406" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_3ef6b2bd-297f-400d-a784-f22f9179c8b7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_187defee-168f-4906-b683-cd10fb3e3ad0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_63c8e0af-d09d-453b-9569-4cacda5ca406" xlink:to="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_187defee-168f-4906-b683-cd10fb3e3ad0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_d3930eb7-d4d8-4b84-96b7-b9dd7bd860f4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_187defee-168f-4906-b683-cd10fb3e3ad0" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_d3930eb7-d4d8-4b84-96b7-b9dd7bd860f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfAdoptionMember_d3930eb7-d4d8-4b84-96b7-b9dd7bd860f4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TypeOfAdoptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_d3930eb7-d4d8-4b84-96b7-b9dd7bd860f4" xlink:to="loc_us-gaap_TypeOfAdoptionMember_d3930eb7-d4d8-4b84-96b7-b9dd7bd860f4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfAdoptionMember_f6ee9f32-fc91-448d-8f3a-7ea7c45a4003" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TypeOfAdoptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_d3930eb7-d4d8-4b84-96b7-b9dd7bd860f4" xlink:to="loc_us-gaap_TypeOfAdoptionMember_f6ee9f32-fc91-448d-8f3a-7ea7c45a4003" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountingStandardsUpdate202006Member_5a1bdb9f-7133-446f-b48e-eb68a0df7fba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountingStandardsUpdate202006Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_f6ee9f32-fc91-448d-8f3a-7ea7c45a4003" xlink:to="loc_us-gaap_AccountingStandardsUpdate202006Member_5a1bdb9f-7133-446f-b48e-eb68a0df7fba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_9989a3b5-0b4f-442b-ade5-4688489e17d3" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_187defee-168f-4906-b683-cd10fb3e3ad0" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_9989a3b5-0b4f-442b-ade5-4688489e17d3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_9989a3b5-0b4f-442b-ade5-4688489e17d3_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_9989a3b5-0b4f-442b-ade5-4688489e17d3" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_9989a3b5-0b4f-442b-ade5-4688489e17d3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_a4d84a24-37c3-43aa-9535-5bdcc0a607ba" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_9989a3b5-0b4f-442b-ade5-4688489e17d3" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_a4d84a24-37c3-43aa-9535-5bdcc0a607ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_c6035d53-7621-4add-85ee-55a6e348d895" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_a4d84a24-37c3-43aa-9535-5bdcc0a607ba" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_c6035d53-7621-4add-85ee-55a6e348d895" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_b73d73b8-bf6e-4aed-915c-3608630120f9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_187defee-168f-4906-b683-cd10fb3e3ad0" xlink:to="loc_us-gaap_DebtInstrumentAxis_b73d73b8-bf6e-4aed-915c-3608630120f9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_b73d73b8-bf6e-4aed-915c-3608630120f9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_b73d73b8-bf6e-4aed-915c-3608630120f9" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_b73d73b8-bf6e-4aed-915c-3608630120f9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e1a01057-5906-487d-beab-5cddec3b6354" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_b73d73b8-bf6e-4aed-915c-3608630120f9" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e1a01057-5906-487d-beab-5cddec3b6354" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2025Member_007218d6-815d-42ed-ab12-483463f9ce96" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_e1a01057-5906-487d-beab-5cddec3b6354" xlink:to="loc_cloud_SeniorConvertibleNotesDue2025Member_007218d6-815d-42ed-ab12-483463f9ce96" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2026Member_dd78fc70-f04f-4033-a1ff-c71cc27fc27c" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_e1a01057-5906-487d-beab-5cddec3b6354" xlink:to="loc_cloud_SeniorConvertibleNotesDue2026Member_dd78fc70-f04f-4033-a1ff-c71cc27fc27c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_9fb1e572-576b-4ce1-ad42-4e36dbea775f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_187defee-168f-4906-b683-cd10fb3e3ad0" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_9fb1e572-576b-4ce1-ad42-4e36dbea775f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_9fb1e572-576b-4ce1-ad42-4e36dbea775f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_9fb1e572-576b-4ce1-ad42-4e36dbea775f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_9fb1e572-576b-4ce1-ad42-4e36dbea775f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_801e60b5-7849-47d6-a92c-df411b773831" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_9fb1e572-576b-4ce1-ad42-4e36dbea775f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_801e60b5-7849-47d6-a92c-df411b773831" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_061be99c-22f8-4d91-bcb0-b06903ff8c50" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_801e60b5-7849-47d6-a92c-df411b773831" xlink:to="loc_us-gaap_ConvertibleDebtMember_061be99c-22f8-4d91-bcb0-b06903ff8c50" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/RevenueDisaggregationofRevenueDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#RevenueDisaggregationofRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/RevenueDisaggregationofRevenueDetails" xlink:type="extended" id="i76cfc144e50840db907fd23d9190b43a_RevenueDisaggregationofRevenueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_81df7fd7-5cce-4c85-b79c-02157402999b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_a66b3982-c1d7-4a6c-9670-48340494a161" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_81df7fd7-5cce-4c85-b79c-02157402999b" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_a66b3982-c1d7-4a6c-9670-48340494a161" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_a73285cb-4ec8-4eff-99b3-71d6a6af9113" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_81df7fd7-5cce-4c85-b79c-02157402999b" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_a73285cb-4ec8-4eff-99b3-71d6a6af9113" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_4ce2c327-198e-421f-8556-64fb1b51ae51" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_81df7fd7-5cce-4c85-b79c-02157402999b" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_4ce2c327-198e-421f-8556-64fb1b51ae51" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_597b0e5e-e9bb-47c2-ab89-9ec35a390886" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_4ce2c327-198e-421f-8556-64fb1b51ae51" xlink:to="loc_srt_StatementGeographicalAxis_597b0e5e-e9bb-47c2-ab89-9ec35a390886" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_597b0e5e-e9bb-47c2-ab89-9ec35a390886_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_597b0e5e-e9bb-47c2-ab89-9ec35a390886" xlink:to="loc_srt_SegmentGeographicalDomain_597b0e5e-e9bb-47c2-ab89-9ec35a390886_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_c327e765-33df-4a65-a0cc-9039642a2885" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_597b0e5e-e9bb-47c2-ab89-9ec35a390886" xlink:to="loc_srt_SegmentGeographicalDomain_c327e765-33df-4a65-a0cc-9039642a2885" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_fbc87401-8748-45b2-8439-9abe39c4099e" xlink:href="https://xbrl.sec.gov/country/2021/country-2021.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_c327e765-33df-4a65-a0cc-9039642a2885" xlink:to="loc_country_US_fbc87401-8748-45b2-8439-9abe39c4099e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EMEAMember_4b570b45-8889-416a-bfa9-d6124ec85ec4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EMEAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_c327e765-33df-4a65-a0cc-9039642a2885" xlink:to="loc_us-gaap_EMEAMember_4b570b45-8889-416a-bfa9-d6124ec85ec4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AsiaPacificMember_e6b8117a-9605-42fc-ad40-4ed6dcfd27bb" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_AsiaPacificMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_c327e765-33df-4a65-a0cc-9039642a2885" xlink:to="loc_srt_AsiaPacificMember_e6b8117a-9605-42fc-ad40-4ed6dcfd27bb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_OtherGeographicalRegionsMember_e5227200-f992-48a9-89d2-55482e4651bd" xlink:href="cloud-20220331.xsd#cloud_OtherGeographicalRegionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_c327e765-33df-4a65-a0cc-9039642a2885" xlink:to="loc_cloud_OtherGeographicalRegionsMember_e5227200-f992-48a9-89d2-55482e4651bd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerSalesChannelAxis_b067d6f5-e9ff-4b3b-88c0-412e17241998" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerSalesChannelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_4ce2c327-198e-421f-8556-64fb1b51ae51" xlink:to="loc_us-gaap_ContractWithCustomerSalesChannelAxis_b067d6f5-e9ff-4b3b-88c0-412e17241998" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerSalesChannelDomain_b067d6f5-e9ff-4b3b-88c0-412e17241998_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerSalesChannelDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelAxis_b067d6f5-e9ff-4b3b-88c0-412e17241998" xlink:to="loc_us-gaap_ContractWithCustomerSalesChannelDomain_b067d6f5-e9ff-4b3b-88c0-412e17241998_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerSalesChannelDomain_32598fc5-fc09-4804-9623-906e9c96e3aa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerSalesChannelDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelAxis_b067d6f5-e9ff-4b3b-88c0-412e17241998" xlink:to="loc_us-gaap_ContractWithCustomerSalesChannelDomain_32598fc5-fc09-4804-9623-906e9c96e3aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesChannelThroughIntermediaryMember_268a9219-9e6e-419a-9b38-6e4540082c1f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SalesChannelThroughIntermediaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelDomain_32598fc5-fc09-4804-9623-906e9c96e3aa" xlink:to="loc_us-gaap_SalesChannelThroughIntermediaryMember_268a9219-9e6e-419a-9b38-6e4540082c1f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesChannelDirectlyToConsumerMember_ac4bb8c6-b2c1-4345-a87e-5657df2c622a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SalesChannelDirectlyToConsumerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelDomain_32598fc5-fc09-4804-9623-906e9c96e3aa" xlink:to="loc_us-gaap_SalesChannelDirectlyToConsumerMember_ac4bb8c6-b2c1-4345-a87e-5657df2c622a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_2f35f9c1-35d8-46c8-9af6-852d9d174055" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_4ce2c327-198e-421f-8556-64fb1b51ae51" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_2f35f9c1-35d8-46c8-9af6-852d9d174055" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_2f35f9c1-35d8-46c8-9af6-852d9d174055_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_2f35f9c1-35d8-46c8-9af6-852d9d174055" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_2f35f9c1-35d8-46c8-9af6-852d9d174055_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_c3d6f101-5011-4d97-a747-a72d3e8105bf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_2f35f9c1-35d8-46c8-9af6-852d9d174055" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_c3d6f101-5011-4d97-a747-a72d3e8105bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeographicConcentrationRiskMember_02bd42da-b736-4384-a35b-71ef2f6c4f55" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GeographicConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_c3d6f101-5011-4d97-a747-a72d3e8105bf" xlink:to="loc_us-gaap_GeographicConcentrationRiskMember_02bd42da-b736-4384-a35b-71ef2f6c4f55" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SalesChannelConcentrationRiskMember_5e5fbf76-5982-45de-995b-db007e9224d8" xlink:href="cloud-20220331.xsd#cloud_SalesChannelConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_c3d6f101-5011-4d97-a747-a72d3e8105bf" xlink:to="loc_cloud_SalesChannelConcentrationRiskMember_5e5fbf76-5982-45de-995b-db007e9224d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_7a424c8f-d5ac-4340-b020-2bd929a56afd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_4ce2c327-198e-421f-8556-64fb1b51ae51" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_7a424c8f-d5ac-4340-b020-2bd929a56afd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_7a424c8f-d5ac-4340-b020-2bd929a56afd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_7a424c8f-d5ac-4340-b020-2bd929a56afd" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_7a424c8f-d5ac-4340-b020-2bd929a56afd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_3803737d-7ae8-404a-b7da-ba369db2dcfc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_7a424c8f-d5ac-4340-b020-2bd929a56afd" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_3803737d-7ae8-404a-b7da-ba369db2dcfc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerMember_50d9ada9-9d58-4f99-bc16-d3af7ba8cb6c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueFromContractWithCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_3803737d-7ae8-404a-b7da-ba369db2dcfc" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerMember_50d9ada9-9d58-4f99-bc16-d3af7ba8cb6c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/RevenueRemainingPerformanceObligationsDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#RevenueRemainingPerformanceObligationsDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/RevenueRemainingPerformanceObligationsDetails" xlink:type="extended" id="i93eeaca0f18f403cada5d2b33d246b5b_RevenueRemainingPerformanceObligationsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_91cd3cd6-11fd-4a74-bb4e-74e502eb093b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_e100a6d8-e93b-4250-8ce0-8be5345c184d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_91cd3cd6-11fd-4a74-bb4e-74e502eb093b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_e100a6d8-e93b-4250-8ce0-8be5345c184d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_4e76bf82-1ad7-44c2-ad72-2c55d1873683" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_91cd3cd6-11fd-4a74-bb4e-74e502eb093b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_4e76bf82-1ad7-44c2-ad72-2c55d1873683" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_6c9e90f3-6c17-412b-bd3c-04324ef6a38b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_91cd3cd6-11fd-4a74-bb4e-74e502eb093b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_6c9e90f3-6c17-412b-bd3c-04324ef6a38b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_55bd0e1b-3d77-43d6-88f8-96adb2d17374" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_91cd3cd6-11fd-4a74-bb4e-74e502eb093b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_55bd0e1b-3d77-43d6-88f8-96adb2d17374" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_d0f263c4-7531-4248-88a3-ce65d30b7845" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_55bd0e1b-3d77-43d6-88f8-96adb2d17374" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_d0f263c4-7531-4248-88a3-ce65d30b7845" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/RevenueRemainingPerformanceObligationsDetails_1" xlink:type="simple" xlink:href="cloud-20220331.xsd#RevenueRemainingPerformanceObligationsDetails_1"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/RevenueRemainingPerformanceObligationsDetails_1" xlink:type="extended" id="ic71c238f3e3e4179803b5592aaf30cb5_RevenueRemainingPerformanceObligationsDetails_1">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_91cd3cd6-11fd-4a74-bb4e-74e502eb093b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_e100a6d8-e93b-4250-8ce0-8be5345c184d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_91cd3cd6-11fd-4a74-bb4e-74e502eb093b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_e100a6d8-e93b-4250-8ce0-8be5345c184d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_4e76bf82-1ad7-44c2-ad72-2c55d1873683" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_91cd3cd6-11fd-4a74-bb4e-74e502eb093b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_4e76bf82-1ad7-44c2-ad72-2c55d1873683" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_6c9e90f3-6c17-412b-bd3c-04324ef6a38b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_91cd3cd6-11fd-4a74-bb4e-74e502eb093b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_6c9e90f3-6c17-412b-bd3c-04324ef6a38b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_55bd0e1b-3d77-43d6-88f8-96adb2d17374" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_91cd3cd6-11fd-4a74-bb4e-74e502eb093b" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_55bd0e1b-3d77-43d6-88f8-96adb2d17374" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/FairValueMeasurementsScheduleofCashandAvailableforsaleDebtSecuritiesAmortizedCostUnrealizedGainsLossesandFairValuebySignificantInvestmentCategoryDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#FairValueMeasurementsScheduleofCashandAvailableforsaleDebtSecuritiesAmortizedCostUnrealizedGainsLossesandFairValuebySignificantInvestmentCategoryDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/FairValueMeasurementsScheduleofCashandAvailableforsaleDebtSecuritiesAmortizedCostUnrealizedGainsLossesandFairValuebySignificantInvestmentCategoryDetails" xlink:type="extended" id="ia3a8ce21002f4671a0b97e48b7e775ff_FairValueMeasurementsScheduleofCashandAvailableforsaleDebtSecuritiesAmortizedCostUnrealizedGainsLossesandFairValuebySignificantInvestmentCategoryDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_1aea955e-cde7-492e-b58a-db58ad60d47c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_1aea955e-cde7-492e-b58a-db58ad60d47c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CashAndCashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax_8c0b1bc8-fe39-4d2a-a889-b9975fdf79eb" xlink:href="cloud-20220331.xsd#cloud_CashAndCashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_cloud_CashAndCashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax_8c0b1bc8-fe39-4d2a-a889-b9975fdf79eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CashAndCashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax_7f5b7ee7-dffb-4838-a4e9-0fec0cf9898b" xlink:href="cloud-20220331.xsd#cloud_CashAndCashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_cloud_CashAndCashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax_7f5b7ee7-dffb-4838-a4e9-0fec0cf9898b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_18d827f0-657d-4565-8c67-bf3545f31905" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_18d827f0-657d-4565-8c67-bf3545f31905" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_c1933035-e16f-498b-ab7c-a54fded26991" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_c1933035-e16f-498b-ab7c-a54fded26991" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_ae5a113f-a3ac-452f-b47a-de5e80698364" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_ae5a113f-a3ac-452f-b47a-de5e80698364" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_00a65d0e-70d4-499c-b9ae-08dcc8eebd1e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_00a65d0e-70d4-499c-b9ae-08dcc8eebd1e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_8361ced1-e0eb-4c34-b035-24c1c3dc6bc9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_8361ced1-e0eb-4c34-b035-24c1c3dc6bc9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_378c2e68-4863-4ad4-919d-0198509f2f89" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_378c2e68-4863-4ad4-919d-0198509f2f89" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CashAndCashEquivalentsAndDebtSecuritiesAvailableForSaleAmortizedCost_780e5b58-b15e-4a56-9068-1b3b485a7bf5" xlink:href="cloud-20220331.xsd#cloud_CashAndCashEquivalentsAndDebtSecuritiesAvailableForSaleAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_cloud_CashAndCashEquivalentsAndDebtSecuritiesAvailableForSaleAmortizedCost_780e5b58-b15e-4a56-9068-1b3b485a7bf5" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CashAndCashEquivalentsAndDebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainBeforeTax_3ac82c7a-f30d-499e-8fb0-715a399cc453" xlink:href="cloud-20220331.xsd#cloud_CashAndCashEquivalentsAndDebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_cloud_CashAndCashEquivalentsAndDebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainBeforeTax_3ac82c7a-f30d-499e-8fb0-715a399cc453" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CashAndCashEquivalentsAndDebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedLossBeforeTax_6b45a307-523c-4dc7-b728-405c784721b4" xlink:href="cloud-20220331.xsd#cloud_CashAndCashEquivalentsAndDebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_cloud_CashAndCashEquivalentsAndDebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedLossBeforeTax_6b45a307-523c-4dc7-b728-405c784721b4" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CashAndCashEquivalentsAndDebtSecuritiesAvailableForSale_499c6ff5-b39d-427c-acc5-f2e6177d8cf7" xlink:href="cloud-20220331.xsd#cloud_CashAndCashEquivalentsAndDebtSecuritiesAvailableForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_cloud_CashAndCashEquivalentsAndDebtSecuritiesAvailableForSale_499c6ff5-b39d-427c-acc5-f2e6177d8cf7" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_460ab4cf-d1bc-4b8c-a96c-76485c6fee20" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_bc8237c5-9db5-4609-b663-9274b8961736" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_460ab4cf-d1bc-4b8c-a96c-76485c6fee20" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_d11db1ee-b899-4e79-bb6f-3ca78e8d0f28" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_460ab4cf-d1bc-4b8c-a96c-76485c6fee20" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_d11db1ee-b899-4e79-bb6f-3ca78e8d0f28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_d11db1ee-b899-4e79-bb6f-3ca78e8d0f28_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_d11db1ee-b899-4e79-bb6f-3ca78e8d0f28" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_d11db1ee-b899-4e79-bb6f-3ca78e8d0f28_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_a711c02b-f30f-4c1b-ad0b-c25d2766c868" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_d11db1ee-b899-4e79-bb6f-3ca78e8d0f28" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_a711c02b-f30f-4c1b-ad0b-c25d2766c868" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsMember_c2096722-23e1-4cdb-aaef-22725a6fcbe8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_a711c02b-f30f-4c1b-ad0b-c25d2766c868" xlink:to="loc_us-gaap_CashAndCashEquivalentsMember_c2096722-23e1-4cdb-aaef-22725a6fcbe8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_DebtSecuritiesAvailableForSaleCurrentMember_e670dd16-e838-4e65-9287-6c0e341c1577" xlink:href="cloud-20220331.xsd#cloud_DebtSecuritiesAvailableForSaleCurrentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_a711c02b-f30f-4c1b-ad0b-c25d2766c868" xlink:to="loc_cloud_DebtSecuritiesAvailableForSaleCurrentMember_e670dd16-e838-4e65-9287-6c0e341c1577" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_RestrictedCashMember_4dad1dca-5f0b-4222-9a4e-c9567e3045ef" xlink:href="cloud-20220331.xsd#cloud_RestrictedCashMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_a711c02b-f30f-4c1b-ad0b-c25d2766c868" xlink:to="loc_cloud_RestrictedCashMember_4dad1dca-5f0b-4222-9a4e-c9567e3045ef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a937255c-ae37-4608-9935-e30754113788" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_460ab4cf-d1bc-4b8c-a96c-76485c6fee20" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a937255c-ae37-4608-9935-e30754113788" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_a937255c-ae37-4608-9935-e30754113788_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a937255c-ae37-4608-9935-e30754113788" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_a937255c-ae37-4608-9935-e30754113788_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_3b68e046-5545-4f2b-bc0f-05303763564f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_a937255c-ae37-4608-9935-e30754113788" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_3b68e046-5545-4f2b-bc0f-05303763564f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_adb4fc3c-e8a8-4664-991a-238e6d65d6ea" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_3b68e046-5545-4f2b-bc0f-05303763564f" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_adb4fc3c-e8a8-4664-991a-238e6d65d6ea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8169e5d2-f79f-414a-a97d-f60dd1a19a30" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_460ab4cf-d1bc-4b8c-a96c-76485c6fee20" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8169e5d2-f79f-414a-a97d-f60dd1a19a30" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8169e5d2-f79f-414a-a97d-f60dd1a19a30_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8169e5d2-f79f-414a-a97d-f60dd1a19a30" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8169e5d2-f79f-414a-a97d-f60dd1a19a30_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_fb736863-bd1c-408b-be1d-79745e84f0c5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8169e5d2-f79f-414a-a97d-f60dd1a19a30" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_fb736863-bd1c-408b-be1d-79745e84f0c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_d3717b41-dbb9-45b0-a59e-1f9d2cbf4d12" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_fb736863-bd1c-408b-be1d-79745e84f0c5" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_d3717b41-dbb9-45b0-a59e-1f9d2cbf4d12" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_690c39ea-722e-48df-979b-c4c38330796a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_fb736863-bd1c-408b-be1d-79745e84f0c5" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_690c39ea-722e-48df-979b-c4c38330796a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_c69a927e-a3ab-4cb7-bdbb-e95d5f146b23" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_460ab4cf-d1bc-4b8c-a96c-76485c6fee20" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_c69a927e-a3ab-4cb7-bdbb-e95d5f146b23" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_c69a927e-a3ab-4cb7-bdbb-e95d5f146b23_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_c69a927e-a3ab-4cb7-bdbb-e95d5f146b23" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_c69a927e-a3ab-4cb7-bdbb-e95d5f146b23_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_8c251ba4-3df0-4567-93b5-a328d9f5f67f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_c69a927e-a3ab-4cb7-bdbb-e95d5f146b23" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_8c251ba4-3df0-4567-93b5-a328d9f5f67f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashMember_0be33c9f-e781-41d7-8ad2-7679362ff71a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_8c251ba4-3df0-4567-93b5-a328d9f5f67f" xlink:to="loc_us-gaap_CashMember_0be33c9f-e781-41d7-8ad2-7679362ff71a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_bcba57f4-6814-4e6a-a877-23e645665c8a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_8c251ba4-3df0-4567-93b5-a328d9f5f67f" xlink:to="loc_us-gaap_MoneyMarketFundsMember_bcba57f4-6814-4e6a-a877-23e645665c8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_ce4309b8-154f-49b1-9e45-af73352d64ac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_460ab4cf-d1bc-4b8c-a96c-76485c6fee20" xlink:to="loc_us-gaap_FinancialInstrumentAxis_ce4309b8-154f-49b1-9e45-af73352d64ac" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ce4309b8-154f-49b1-9e45-af73352d64ac_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_ce4309b8-154f-49b1-9e45-af73352d64ac" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ce4309b8-154f-49b1-9e45-af73352d64ac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_d710b0f7-d58a-4549-8774-7975a407abde" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_ce4309b8-154f-49b1-9e45-af73352d64ac" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_d710b0f7-d58a-4549-8774-7975a407abde" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_42eaeae8-1207-424d-8a7f-d19f8383408c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CorporateBondSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_d710b0f7-d58a-4549-8774-7975a407abde" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_42eaeae8-1207-424d-8a7f-d19f8383408c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_8cc78505-ee7b-4a9f-a999-6e7803eead8f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_d710b0f7-d58a-4549-8774-7975a407abde" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_8cc78505-ee7b-4a9f-a999-6e7803eead8f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperMember_cc624c18-8ed5-4f8c-989c-eac887d2a3c9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommercialPaperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_d710b0f7-d58a-4549-8774-7975a407abde" xlink:to="loc_us-gaap_CommercialPaperMember_cc624c18-8ed5-4f8c-989c-eac887d2a3c9" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/FairValueMeasurementsNarrativesDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#FairValueMeasurementsNarrativesDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/FairValueMeasurementsNarrativesDetails" xlink:type="extended" id="id656f61f01b543b8a45730480c5147b5_FairValueMeasurementsNarrativesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_88424a10-7b14-4c3a-adaf-8668eec7f423" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_7577fb8d-1cb8-45b7-8189-c23ffe8b6daf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_88424a10-7b14-4c3a-adaf-8668eec7f423" xlink:to="loc_us-gaap_RestrictedCash_7577fb8d-1cb8-45b7-8189-c23ffe8b6daf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_BusinessCombinationConsiderationPayable_388ba8fc-4191-42c1-97b0-e82f3d30a469" xlink:href="cloud-20220331.xsd#cloud_BusinessCombinationConsiderationPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_88424a10-7b14-4c3a-adaf-8668eec7f423" xlink:to="loc_cloud_BusinessCombinationConsiderationPayable_388ba8fc-4191-42c1-97b0-e82f3d30a469" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CashAndCashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax_7b81377e-6ab7-4f94-8040-e96b0ef9af98" xlink:href="cloud-20220331.xsd#cloud_CashAndCashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_88424a10-7b14-4c3a-adaf-8668eec7f423" xlink:to="loc_cloud_CashAndCashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax_7b81377e-6ab7-4f94-8040-e96b0ef9af98" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CashAndCashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax_a503fda7-8e08-4e07-a18a-4102da84f230" xlink:href="cloud-20220331.xsd#cloud_CashAndCashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_88424a10-7b14-4c3a-adaf-8668eec7f423" xlink:to="loc_cloud_CashAndCashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax_a503fda7-8e08-4e07-a18a-4102da84f230" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_fd51a79e-e756-4042-99b4-d19211ee72b1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_88424a10-7b14-4c3a-adaf-8668eec7f423" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_fd51a79e-e756-4042-99b4-d19211ee72b1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterOneYearAmortizedCost_dc4e632a-65c5-458f-aeab-fc846b831bd9" xlink:href="cloud-20220331.xsd#cloud_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterOneYearAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_88424a10-7b14-4c3a-adaf-8668eec7f423" xlink:to="loc_cloud_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterOneYearAmortizedCost_dc4e632a-65c5-458f-aeab-fc846b831bd9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_43167bdc-278c-424b-a24f-d5264a951a31" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_88424a10-7b14-4c3a-adaf-8668eec7f423" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_43167bdc-278c-424b-a24f-d5264a951a31" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFairValue_7f610385-4ba5-4707-a859-1a778d689d42" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_88424a10-7b14-4c3a-adaf-8668eec7f423" xlink:to="loc_us-gaap_DebtInstrumentFairValue_7f610385-4ba5-4707-a859-1a778d689d42" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_813e1e4a-dbc3-4378-857b-b26c63eacaf7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_88424a10-7b14-4c3a-adaf-8668eec7f423" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_813e1e4a-dbc3-4378-857b-b26c63eacaf7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_6823617f-b4f0-407a-892e-9e4965570fda" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_813e1e4a-dbc3-4378-857b-b26c63eacaf7" xlink:to="loc_us-gaap_CreditFacilityAxis_6823617f-b4f0-407a-892e-9e4965570fda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_6823617f-b4f0-407a-892e-9e4965570fda_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_6823617f-b4f0-407a-892e-9e4965570fda" xlink:to="loc_us-gaap_CreditFacilityDomain_6823617f-b4f0-407a-892e-9e4965570fda_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_2a68b1e5-4bc9-4370-bd8b-4e26fe92b590" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_6823617f-b4f0-407a-892e-9e4965570fda" xlink:to="loc_us-gaap_CreditFacilityDomain_2a68b1e5-4bc9-4370-bd8b-4e26fe92b590" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StandbyLettersOfCreditMember_2deabac8-ef6f-4981-b49f-4d6a40e2d2d4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StandbyLettersOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_2a68b1e5-4bc9-4370-bd8b-4e26fe92b590" xlink:to="loc_us-gaap_StandbyLettersOfCreditMember_2deabac8-ef6f-4981-b49f-4d6a40e2d2d4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_0a03966f-f19d-4090-a471-5c0dda900b8e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_813e1e4a-dbc3-4378-857b-b26c63eacaf7" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_0a03966f-f19d-4090-a471-5c0dda900b8e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_0a03966f-f19d-4090-a471-5c0dda900b8e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_0a03966f-f19d-4090-a471-5c0dda900b8e" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_0a03966f-f19d-4090-a471-5c0dda900b8e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_5e8bfbfb-56c6-4b23-bb6b-a5e977215f57" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_0a03966f-f19d-4090-a471-5c0dda900b8e" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_5e8bfbfb-56c6-4b23-bb6b-a5e977215f57" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_3c0755d6-accc-4fff-966c-14a91f726510" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_5e8bfbfb-56c6-4b23-bb6b-a5e977215f57" xlink:to="loc_us-gaap_MoneyMarketFundsMember_3c0755d6-accc-4fff-966c-14a91f726510" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_e29dbf5f-d4cc-490a-90eb-2d4e8da4e2b5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_813e1e4a-dbc3-4378-857b-b26c63eacaf7" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_e29dbf5f-d4cc-490a-90eb-2d4e8da4e2b5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_e29dbf5f-d4cc-490a-90eb-2d4e8da4e2b5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_e29dbf5f-d4cc-490a-90eb-2d4e8da4e2b5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_e29dbf5f-d4cc-490a-90eb-2d4e8da4e2b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_4e827543-42b3-48e1-bfd8-6787eed9c326" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_e29dbf5f-d4cc-490a-90eb-2d4e8da4e2b5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_4e827543-42b3-48e1-bfd8-6787eed9c326" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_a850a076-123f-442e-8141-6b223708f774" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_4e827543-42b3-48e1-bfd8-6787eed9c326" xlink:to="loc_us-gaap_ConvertibleDebtMember_a850a076-123f-442e-8141-6b223708f774" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_9d020a63-6059-402b-afc5-38c75e5b0347" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_813e1e4a-dbc3-4378-857b-b26c63eacaf7" xlink:to="loc_us-gaap_DebtInstrumentAxis_9d020a63-6059-402b-afc5-38c75e5b0347" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9d020a63-6059-402b-afc5-38c75e5b0347_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_9d020a63-6059-402b-afc5-38c75e5b0347" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9d020a63-6059-402b-afc5-38c75e5b0347_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_fb2a3d0f-e6c4-4ccb-9d60-de6977fc07cf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_9d020a63-6059-402b-afc5-38c75e5b0347" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_fb2a3d0f-e6c4-4ccb-9d60-de6977fc07cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2026Member_da4597fe-8ac1-493f-b01f-857f1874f3d3" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fb2a3d0f-e6c4-4ccb-9d60-de6977fc07cf" xlink:to="loc_cloud_SeniorConvertibleNotesDue2026Member_da4597fe-8ac1-493f-b01f-857f1874f3d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_c99bb480-0dc2-47cb-b99a-a2e22efb7583" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_813e1e4a-dbc3-4378-857b-b26c63eacaf7" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_c99bb480-0dc2-47cb-b99a-a2e22efb7583" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c99bb480-0dc2-47cb-b99a-a2e22efb7583_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_c99bb480-0dc2-47cb-b99a-a2e22efb7583" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c99bb480-0dc2-47cb-b99a-a2e22efb7583_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bbff739f-f7b0-449d-8d67-7e310713f949" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_c99bb480-0dc2-47cb-b99a-a2e22efb7583" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bbff739f-f7b0-449d-8d67-7e310713f949" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_VectrixIncMember_9c0380d7-48f6-40a5-8660-11c7def327a7" xlink:href="cloud-20220331.xsd#cloud_VectrixIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bbff739f-f7b0-449d-8d67-7e310713f949" xlink:to="loc_cloud_VectrixIncMember_9c0380d7-48f6-40a5-8660-11c7def327a7" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/BalanceSheetComponentsPropertyandEquipmentNetDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#BalanceSheetComponentsPropertyandEquipmentNetDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/BalanceSheetComponentsPropertyandEquipmentNetDetails" xlink:type="extended" id="icd5e6cdf195f4bb3b0dcd159d0ed3d83_BalanceSheetComponentsPropertyandEquipmentNetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_07b8f3e3-788a-4f9b-b619-dc70a9ea1753" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_500aa7c2-1616-4e21-859a-a4c90d39c49d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_07b8f3e3-788a-4f9b-b619-dc70a9ea1753" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_500aa7c2-1616-4e21-859a-a4c90d39c49d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_f053a2e2-4f75-4bfc-a194-b055ced7f753" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_07b8f3e3-788a-4f9b-b619-dc70a9ea1753" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_f053a2e2-4f75-4bfc-a194-b055ced7f753" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_d7d76a16-2b7f-418a-b3fa-75495b82c5b6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_07b8f3e3-788a-4f9b-b619-dc70a9ea1753" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_d7d76a16-2b7f-418a-b3fa-75495b82c5b6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_53841437-a8d1-4c70-86e2-54c6f8959297" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_07b8f3e3-788a-4f9b-b619-dc70a9ea1753" xlink:to="loc_us-gaap_Depreciation_53841437-a8d1-4c70-86e2-54c6f8959297" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_b6c2d863-6075-45f1-999a-ef1edd78998e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_07b8f3e3-788a-4f9b-b619-dc70a9ea1753" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_b6c2d863-6075-45f1-999a-ef1edd78998e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_051f385d-00ef-4abc-a02e-b94243563b71" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_b6c2d863-6075-45f1-999a-ef1edd78998e" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_051f385d-00ef-4abc-a02e-b94243563b71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_051f385d-00ef-4abc-a02e-b94243563b71_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_051f385d-00ef-4abc-a02e-b94243563b71" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_051f385d-00ef-4abc-a02e-b94243563b71_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ef62749e-5785-4e5e-86d4-0cf556e73a7a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_051f385d-00ef-4abc-a02e-b94243563b71" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ef62749e-5785-4e5e-86d4-0cf556e73a7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TechnologyEquipmentMember_261f583e-dbeb-4b70-b76a-bada28d6f120" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TechnologyEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ef62749e-5785-4e5e-86d4-0cf556e73a7a" xlink:to="loc_us-gaap_TechnologyEquipmentMember_261f583e-dbeb-4b70-b76a-bada28d6f120" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_3815b94a-53a3-4d28-9615-819f1f6c4215" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ef62749e-5785-4e5e-86d4-0cf556e73a7a" xlink:to="loc_us-gaap_ConstructionInProgressMember_3815b94a-53a3-4d28-9615-819f1f6c4215" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SoftwareDevelopmentMember_ddba88ae-e11d-45c4-836e-72896f1704ad" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SoftwareDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ef62749e-5785-4e5e-86d4-0cf556e73a7a" xlink:to="loc_us-gaap_SoftwareDevelopmentMember_ddba88ae-e11d-45c4-836e-72896f1704ad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OfficeEquipmentMember_2c30cb25-b1b5-49e3-bfcd-09e4dce14882" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OfficeEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ef62749e-5785-4e5e-86d4-0cf556e73a7a" xlink:to="loc_us-gaap_OfficeEquipmentMember_2c30cb25-b1b5-49e3-bfcd-09e4dce14882" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_cbdcfbe3-cf0e-4069-a648-6fef2a4b86cf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FurnitureAndFixturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ef62749e-5785-4e5e-86d4-0cf556e73a7a" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_cbdcfbe3-cf0e-4069-a648-6fef2a4b86cf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_4cd6711c-1931-401e-a96a-7ae53b96b26f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SoftwareAndSoftwareDevelopmentCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ef62749e-5785-4e5e-86d4-0cf556e73a7a" xlink:to="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_4cd6711c-1931-401e-a96a-7ae53b96b26f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_c5124a57-847a-4540-9ada-dc6b1116eb02" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ef62749e-5785-4e5e-86d4-0cf556e73a7a" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_c5124a57-847a-4540-9ada-dc6b1116eb02" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RemediationPropertyForSaleAbandonmentOrDisposalMember_8b6be767-58e5-42c5-bc3f-ed6e749140d1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RemediationPropertyForSaleAbandonmentOrDisposalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ef62749e-5785-4e5e-86d4-0cf556e73a7a" xlink:to="loc_us-gaap_RemediationPropertyForSaleAbandonmentOrDisposalMember_8b6be767-58e5-42c5-bc3f-ed6e749140d1" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/BalanceSheetComponentsGoodwillDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#BalanceSheetComponentsGoodwillDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/BalanceSheetComponentsGoodwillDetails" xlink:type="extended" id="ibc3fcc844d394597aef6b6179f449c08_BalanceSheetComponentsGoodwillDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_646a5e6b-b116-4b62-9b6a-dd8c30fad527" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAcquiredDuringPeriod_33cfa756-2258-49a2-b514-ec3ec87017e5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GoodwillAcquiredDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_646a5e6b-b116-4b62-9b6a-dd8c30fad527" xlink:to="loc_us-gaap_GoodwillAcquiredDuringPeriod_33cfa756-2258-49a2-b514-ec3ec87017e5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5d964cbe-28b7-4f54-bc4b-45557749b7dc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_646a5e6b-b116-4b62-9b6a-dd8c30fad527" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5d964cbe-28b7-4f54-bc4b-45557749b7dc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_7cf97ce8-79b3-44b8-854b-10df30a60257" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5d964cbe-28b7-4f54-bc4b-45557749b7dc" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_7cf97ce8-79b3-44b8-854b-10df30a60257" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7cf97ce8-79b3-44b8-854b-10df30a60257_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_7cf97ce8-79b3-44b8-854b-10df30a60257" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7cf97ce8-79b3-44b8-854b-10df30a60257_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7d721415-d742-47b6-9c16-d66969d62151" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_7cf97ce8-79b3-44b8-854b-10df30a60257" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7d721415-d742-47b6-9c16-d66969d62151" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_VectrixIncMember_862109cc-1189-4792-9c54-403443633130" xlink:href="cloud-20220331.xsd#cloud_VectrixIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7d721415-d742-47b6-9c16-d66969d62151" xlink:to="loc_cloud_VectrixIncMember_862109cc-1189-4792-9c54-403443633130" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/BalanceSheetComponentsAcquiredIntangibleAssetsNetDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#BalanceSheetComponentsAcquiredIntangibleAssetsNetDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/BalanceSheetComponentsAcquiredIntangibleAssetsNetDetails" xlink:type="extended" id="id5097273e1024abf947564358487b25c_BalanceSheetComponentsAcquiredIntangibleAssetsNetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_d2505244-b788-4333-bbb6-b01581c157f0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_48cbb443-bc0c-4885-922f-2e3931630461" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_d2505244-b788-4333-bbb6-b01581c157f0" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_48cbb443-bc0c-4885-922f-2e3931630461" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_20ad9b67-57f7-4746-ab7c-f3420ec5d4ac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_d2505244-b788-4333-bbb6-b01581c157f0" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_20ad9b67-57f7-4746-ab7c-f3420ec5d4ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_f0c58b84-c295-4231-8a30-60df7d9a0284" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_d2505244-b788-4333-bbb6-b01581c157f0" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_f0c58b84-c295-4231-8a30-60df7d9a0284" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_6ca635e3-e078-49c6-ac3f-64b357278a33" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_d2505244-b788-4333-bbb6-b01581c157f0" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_6ca635e3-e078-49c6-ac3f-64b357278a33" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_44aa1307-e474-4f56-9a77-e27a94c45e3b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_d2505244-b788-4333-bbb6-b01581c157f0" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_44aa1307-e474-4f56-9a77-e27a94c45e3b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_a7d088dd-e9ed-4079-afab-e2cfd5522d30" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_44aa1307-e474-4f56-9a77-e27a94c45e3b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_a7d088dd-e9ed-4079-afab-e2cfd5522d30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a7d088dd-e9ed-4079-afab-e2cfd5522d30_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_a7d088dd-e9ed-4079-afab-e2cfd5522d30" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a7d088dd-e9ed-4079-afab-e2cfd5522d30_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_19f02dca-9d7a-4ca6-8853-c2144de17667" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_a7d088dd-e9ed-4079-afab-e2cfd5522d30" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_19f02dca-9d7a-4ca6-8853-c2144de17667" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_d6bfc316-df1f-42b2-bfb9-8900b77719ec" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_19f02dca-9d7a-4ca6-8853-c2144de17667" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_d6bfc316-df1f-42b2-bfb9-8900b77719ec" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/LeasesNarrativesDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#LeasesNarrativesDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/LeasesNarrativesDetails" xlink:type="extended" id="i803dcd59f9554490a81cae20ae536417_LeasesNarrativesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_bacd87d8-f461-48ac-be5f-35eea581983f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_c82a8930-e783-4deb-b262-ebdc774dcb2f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseRemainingLeaseTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bacd87d8-f461-48ac-be5f-35eea581983f" xlink:to="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_c82a8930-e783-4deb-b262-ebdc774dcb2f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubleaseIncome_b5133be0-8c80-4f12-8d1e-da421de00743" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubleaseIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bacd87d8-f461-48ac-be5f-35eea581983f" xlink:to="loc_us-gaap_SubleaseIncome_b5133be0-8c80-4f12-8d1e-da421de00743" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_LesseeOperatingLeaseLeaseNotYetCommencedUndiscountedAmount_a1e75775-1ffe-4bad-8ae8-94bc4af1dce6" xlink:href="cloud-20220331.xsd#cloud_LesseeOperatingLeaseLeaseNotYetCommencedUndiscountedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bacd87d8-f461-48ac-be5f-35eea581983f" xlink:to="loc_cloud_LesseeOperatingLeaseLeaseNotYetCommencedUndiscountedAmount_a1e75775-1ffe-4bad-8ae8-94bc4af1dce6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1_a5dd9828-5164-49cf-bb69-7dbd67042a5d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bacd87d8-f461-48ac-be5f-35eea581983f" xlink:to="loc_us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1_a5dd9828-5164-49cf-bb69-7dbd67042a5d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_2794f28c-2cf6-4e08-926f-85f9afb8c2ca" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bacd87d8-f461-48ac-be5f-35eea581983f" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_2794f28c-2cf6-4e08-926f-85f9afb8c2ca" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_234abbac-ed50-4aba-9d4c-07802b8e2bb4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bacd87d8-f461-48ac-be5f-35eea581983f" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_234abbac-ed50-4aba-9d4c-07802b8e2bb4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_9b0064c2-ae92-4058-8e0c-6282f597046a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bacd87d8-f461-48ac-be5f-35eea581983f" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_9b0064c2-ae92-4058-8e0c-6282f597046a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseContractualTermAxis_86be6f6e-9a76-449d-859c-3258bca0a8f1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LeaseContractualTermAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_9b0064c2-ae92-4058-8e0c-6282f597046a" xlink:to="loc_us-gaap_LeaseContractualTermAxis_86be6f6e-9a76-449d-859c-3258bca0a8f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseContractualTermDomain_86be6f6e-9a76-449d-859c-3258bca0a8f1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LeaseContractualTermDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LeaseContractualTermAxis_86be6f6e-9a76-449d-859c-3258bca0a8f1" xlink:to="loc_us-gaap_LeaseContractualTermDomain_86be6f6e-9a76-449d-859c-3258bca0a8f1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseContractualTermDomain_9a0d6f6c-c9c7-430c-ad9b-d9d82df37878" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LeaseContractualTermDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LeaseContractualTermAxis_86be6f6e-9a76-449d-859c-3258bca0a8f1" xlink:to="loc_us-gaap_LeaseContractualTermDomain_9a0d6f6c-c9c7-430c-ad9b-d9d82df37878" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CoLocationAssetLeaseMember_150f8875-8413-4ecd-b2c5-21fb8db3a894" xlink:href="cloud-20220331.xsd#cloud_CoLocationAssetLeaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseContractualTermDomain_9a0d6f6c-c9c7-430c-ad9b-d9d82df37878" xlink:to="loc_cloud_CoLocationAssetLeaseMember_150f8875-8413-4ecd-b2c5-21fb8db3a894" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/Debt2026ConvertibleSeniorNotesDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#Debt2026ConvertibleSeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/Debt2026ConvertibleSeniorNotesDetails" xlink:type="extended" id="i959b93898ef34677a076c83a940ef2a9_Debt2026ConvertibleSeniorNotesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_385c7c8b-df73-4ca2-9a70-118e74ec03e0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_385c7c8b-df73-4ca2-9a70-118e74ec03e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_DebtInstrumentFaceAmountAdditionalPrincipalIssuable_9c2c7071-00fc-4b06-b1d8-bd419129b877" xlink:href="cloud-20220331.xsd#cloud_DebtInstrumentFaceAmountAdditionalPrincipalIssuable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_cloud_DebtInstrumentFaceAmountAdditionalPrincipalIssuable_9c2c7071-00fc-4b06-b1d8-bd419129b877" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromConvertibleDebt_cd4c6c25-4f44-434f-b07d-3b7aacc3014c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_us-gaap_ProceedsFromConvertibleDebt_cd4c6c25-4f44-434f-b07d-3b7aacc3014c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_abdca057-2b02-44a3-8855-39abaa690aec" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_abdca057-2b02-44a3-8855-39abaa690aec" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_61d437c0-9a6e-4f47-abf9-6fee78edd505" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionRatio1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_61d437c0-9a6e-4f47-abf9-6fee78edd505" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_82bd5e90-3d70-42da-afb4-821ca579057d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_82bd5e90-3d70-42da-afb4-821ca579057d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_be1ee20f-dfd5-436d-8245-b749d6fe4ec0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_be1ee20f-dfd5-436d-8245-b749d6fe4ec0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_43fcecf8-1ae3-4733-89d5-8d0f34423b9e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_43fcecf8-1ae3-4733-89d5-8d0f34423b9e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_bfe2ca62-3553-4275-a428-2e526dcaab95" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_bfe2ca62-3553-4275-a428-2e526dcaab95" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_8367b854-43ea-4cf8-9d34-40958014f538" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_8367b854-43ea-4cf8-9d34-40958014f538" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_DebtInstrumentCovenantMinimumRedeemableFaceAmount_08aebb76-39c4-45dc-a156-5790045d0d9b" xlink:href="cloud-20220331.xsd#cloud_DebtInstrumentCovenantMinimumRedeemableFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_cloud_DebtInstrumentCovenantMinimumRedeemableFaceAmount_08aebb76-39c4-45dc-a156-5790045d0d9b" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharePrice_5e42816d-9d54-4550-9bc4-472ec9419757" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_us-gaap_SharePrice_5e42816d-9d54-4550-9bc4-472ec9419757" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1_4804b31f-5bc9-4d7d-a5c1-ba056031f731" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1_4804b31f-5bc9-4d7d-a5c1-ba056031f731" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_850d331c-7ac1-45e9-9b83-e408fc17cc41" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5918cd92-9338-4cb5-9155-8e501ef42958" xlink:to="loc_us-gaap_DebtInstrumentTable_850d331c-7ac1-45e9-9b83-e408fc17cc41" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_205ec28d-0660-4467-83ca-92fe6452c236" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_850d331c-7ac1-45e9-9b83-e408fc17cc41" xlink:to="loc_us-gaap_DebtInstrumentAxis_205ec28d-0660-4467-83ca-92fe6452c236" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_205ec28d-0660-4467-83ca-92fe6452c236_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_205ec28d-0660-4467-83ca-92fe6452c236" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_205ec28d-0660-4467-83ca-92fe6452c236_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e4e51b69-7196-449f-bb17-2600cb15f13f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_205ec28d-0660-4467-83ca-92fe6452c236" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e4e51b69-7196-449f-bb17-2600cb15f13f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2026Member_3d417467-908f-4405-9a27-0c7bd0c5cba7" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_e4e51b69-7196-449f-bb17-2600cb15f13f" xlink:to="loc_cloud_SeniorConvertibleNotesDue2026Member_3d417467-908f-4405-9a27-0c7bd0c5cba7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_7556d2c7-5b6d-4a5b-ae64-b0b0eba217dc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_850d331c-7ac1-45e9-9b83-e408fc17cc41" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_7556d2c7-5b6d-4a5b-ae64-b0b0eba217dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_7556d2c7-5b6d-4a5b-ae64-b0b0eba217dc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_7556d2c7-5b6d-4a5b-ae64-b0b0eba217dc" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_7556d2c7-5b6d-4a5b-ae64-b0b0eba217dc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_03e3d457-6af1-4444-b54b-e6335fe3599c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_7556d2c7-5b6d-4a5b-ae64-b0b0eba217dc" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_03e3d457-6af1-4444-b54b-e6335fe3599c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_0d37d707-8da2-484e-be86-e19d7d7f9f61" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_03e3d457-6af1-4444-b54b-e6335fe3599c" xlink:to="loc_us-gaap_ConvertibleDebtMember_0d37d707-8da2-484e-be86-e19d7d7f9f61" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionByUniqueDescriptionAxis_03d7de4c-b9c2-4d15-bf85-6a898de1cb65" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtConversionByUniqueDescriptionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_850d331c-7ac1-45e9-9b83-e408fc17cc41" xlink:to="loc_us-gaap_DebtConversionByUniqueDescriptionAxis_03d7de4c-b9c2-4d15-bf85-6a898de1cb65" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionNameDomain_03d7de4c-b9c2-4d15-bf85-6a898de1cb65_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtConversionNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtConversionByUniqueDescriptionAxis_03d7de4c-b9c2-4d15-bf85-6a898de1cb65" xlink:to="loc_us-gaap_DebtConversionNameDomain_03d7de4c-b9c2-4d15-bf85-6a898de1cb65_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionNameDomain_09df906c-439f-4b80-aebd-11af974b857c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtConversionNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtConversionByUniqueDescriptionAxis_03d7de4c-b9c2-4d15-bf85-6a898de1cb65" xlink:to="loc_us-gaap_DebtConversionNameDomain_09df906c-439f-4b80-aebd-11af974b857c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ScenarioOneMember_e561c195-1f5c-46c9-aa1c-eeb7cb442848" xlink:href="cloud-20220331.xsd#cloud_ScenarioOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtConversionNameDomain_09df906c-439f-4b80-aebd-11af974b857c" xlink:to="loc_cloud_ScenarioOneMember_e561c195-1f5c-46c9-aa1c-eeb7cb442848" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ScenarioTwoMember_cf382bed-3776-46f7-bc9f-1695cdfdaa2b" xlink:href="cloud-20220331.xsd#cloud_ScenarioTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtConversionNameDomain_09df906c-439f-4b80-aebd-11af974b857c" xlink:to="loc_cloud_ScenarioTwoMember_cf382bed-3776-46f7-bc9f-1695cdfdaa2b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/Debt2026CappedCallTransactionsDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#Debt2026CappedCallTransactionsDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/Debt2026CappedCallTransactionsDetails" xlink:type="extended" id="i1d3ba9143ec44d4eb2aca97abc01cceb_Debt2026CappedCallTransactionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_1b7ca2cb-338c-4c9f-bcf4-45775f62e5ab" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionIndexedToIssuersEquityStrikePrice1_5359b021-393f-4546-b5a2-5d1077d4bdd1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OptionIndexedToIssuersEquityStrikePrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1b7ca2cb-338c-4c9f-bcf4-45775f62e5ab" xlink:to="loc_us-gaap_OptionIndexedToIssuersEquityStrikePrice1_5359b021-393f-4546-b5a2-5d1077d4bdd1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CappedCallInitialCapPrice_c8e36759-82a2-4997-a0d2-76923abc4d83" xlink:href="cloud-20220331.xsd#cloud_CappedCallInitialCapPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1b7ca2cb-338c-4c9f-bcf4-45775f62e5ab" xlink:to="loc_cloud_CappedCallInitialCapPrice_c8e36759-82a2-4997-a0d2-76923abc4d83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SharesCoveredByCappedCalls_e7faa11d-def3-450d-b66f-fbca4cdc4b37" xlink:href="cloud-20220331.xsd#cloud_SharesCoveredByCappedCalls"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1b7ca2cb-338c-4c9f-bcf4-45775f62e5ab" xlink:to="loc_cloud_SharesCoveredByCappedCalls_e7faa11d-def3-450d-b66f-fbca4cdc4b37" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_AdjustmentsToAdditionalPaidInCapitalPurchasesOfCappedCallsRelatedToConvertibleDebt_d9e7f85d-899a-479b-bdb6-356baa9b7a21" xlink:href="cloud-20220331.xsd#cloud_AdjustmentsToAdditionalPaidInCapitalPurchasesOfCappedCallsRelatedToConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1b7ca2cb-338c-4c9f-bcf4-45775f62e5ab" xlink:to="loc_cloud_AdjustmentsToAdditionalPaidInCapitalPurchasesOfCappedCallsRelatedToConvertibleDebt_d9e7f85d-899a-479b-bdb6-356baa9b7a21" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_855f1141-b321-4952-9318-0f07e935669c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1b7ca2cb-338c-4c9f-bcf4-45775f62e5ab" xlink:to="loc_us-gaap_DebtInstrumentTable_855f1141-b321-4952-9318-0f07e935669c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_d4001bd1-8004-4dda-9d8d-4616babc24b4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_855f1141-b321-4952-9318-0f07e935669c" xlink:to="loc_us-gaap_DebtInstrumentAxis_d4001bd1-8004-4dda-9d8d-4616babc24b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_d4001bd1-8004-4dda-9d8d-4616babc24b4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_d4001bd1-8004-4dda-9d8d-4616babc24b4" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_d4001bd1-8004-4dda-9d8d-4616babc24b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_6ed1a1d8-4b3b-4f3b-828c-9830edd26a56" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_d4001bd1-8004-4dda-9d8d-4616babc24b4" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_6ed1a1d8-4b3b-4f3b-828c-9830edd26a56" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2026Member_e3f78c0a-6cb5-4dc7-9560-47d896efb618" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6ed1a1d8-4b3b-4f3b-828c-9830edd26a56" xlink:to="loc_cloud_SeniorConvertibleNotesDue2026Member_e3f78c0a-6cb5-4dc7-9560-47d896efb618" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_d9cd9e27-b1f7-40f8-83d2-f842fbf30ba5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_855f1141-b321-4952-9318-0f07e935669c" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_d9cd9e27-b1f7-40f8-83d2-f842fbf30ba5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_d9cd9e27-b1f7-40f8-83d2-f842fbf30ba5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_d9cd9e27-b1f7-40f8-83d2-f842fbf30ba5" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_d9cd9e27-b1f7-40f8-83d2-f842fbf30ba5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_170f9c0f-631a-4384-8aad-55f32bef67cb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_d9cd9e27-b1f7-40f8-83d2-f842fbf30ba5" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_170f9c0f-631a-4384-8aad-55f32bef67cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CappedCallsMember_b3d74b59-e2b3-4775-a363-1b02cf858ac2" xlink:href="cloud-20220331.xsd#cloud_CappedCallsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_170f9c0f-631a-4384-8aad-55f32bef67cb" xlink:to="loc_cloud_CappedCallsMember_b3d74b59-e2b3-4775-a363-1b02cf858ac2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_29997e1c-97b8-426b-b5e0-b0dc53a78698" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_855f1141-b321-4952-9318-0f07e935669c" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_29997e1c-97b8-426b-b5e0-b0dc53a78698" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_29997e1c-97b8-426b-b5e0-b0dc53a78698_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_29997e1c-97b8-426b-b5e0-b0dc53a78698" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_29997e1c-97b8-426b-b5e0-b0dc53a78698_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_573ccd09-d971-40a9-8042-6f72e59192ed" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_29997e1c-97b8-426b-b5e0-b0dc53a78698" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_573ccd09-d971-40a9-8042-6f72e59192ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_de55d698-0b68-4c20-83ee-d6297505f072" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_573ccd09-d971-40a9-8042-6f72e59192ed" xlink:to="loc_us-gaap_ConvertibleDebtMember_de55d698-0b68-4c20-83ee-d6297505f072" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionAxis_7af3ca8b-5f42-4d29-a939-10d91ad3b99f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PositionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_855f1141-b321-4952-9318-0f07e935669c" xlink:to="loc_us-gaap_PositionAxis_7af3ca8b-5f42-4d29-a939-10d91ad3b99f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionDomain_7af3ca8b-5f42-4d29-a939-10d91ad3b99f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PositionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PositionAxis_7af3ca8b-5f42-4d29-a939-10d91ad3b99f" xlink:to="loc_us-gaap_PositionDomain_7af3ca8b-5f42-4d29-a939-10d91ad3b99f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionDomain_32a65414-110d-44d4-9edb-0362fbfa0790" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PositionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PositionAxis_7af3ca8b-5f42-4d29-a939-10d91ad3b99f" xlink:to="loc_us-gaap_PositionDomain_32a65414-110d-44d4-9edb-0362fbfa0790" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongMember_059fdec7-b953-4586-a0e6-7660ac77213e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PositionDomain_32a65414-110d-44d4-9edb-0362fbfa0790" xlink:to="loc_us-gaap_LongMember_059fdec7-b953-4586-a0e6-7660ac77213e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_442bfd5c-3f84-4616-ae1e-e1ac3584f391" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_855f1141-b321-4952-9318-0f07e935669c" xlink:to="loc_us-gaap_StatementClassOfStockAxis_442bfd5c-3f84-4616-ae1e-e1ac3584f391" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_442bfd5c-3f84-4616-ae1e-e1ac3584f391_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_442bfd5c-3f84-4616-ae1e-e1ac3584f391" xlink:to="loc_us-gaap_ClassOfStockDomain_442bfd5c-3f84-4616-ae1e-e1ac3584f391_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_cf72d32c-b320-4aaf-a6b6-dbea84cebaca" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_442bfd5c-3f84-4616-ae1e-e1ac3584f391" xlink:to="loc_us-gaap_ClassOfStockDomain_cf72d32c-b320-4aaf-a6b6-dbea84cebaca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_fe4746dc-2928-421c-9c03-0ed48c9bb26f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_cf72d32c-b320-4aaf-a6b6-dbea84cebaca" xlink:to="loc_us-gaap_CommonClassAMember_fe4746dc-2928-421c-9c03-0ed48c9bb26f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/Debt2025ConvertibleSeniorNotesDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#Debt2025ConvertibleSeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/Debt2025ConvertibleSeniorNotesDetails" xlink:type="extended" id="ib1a4a2ace7834fbcae722ae0fb7c0e6e_Debt2025ConvertibleSeniorNotesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_e37f0ce0-58a8-4ae0-bd13-dd521ec36279" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_e37f0ce0-58a8-4ae0-bd13-dd521ec36279" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_DebtInstrumentFaceAmountAdditionalPrincipalIssuable_2e953de7-c944-47a7-ae75-622cf3e36825" xlink:href="cloud-20220331.xsd#cloud_DebtInstrumentFaceAmountAdditionalPrincipalIssuable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_cloud_DebtInstrumentFaceAmountAdditionalPrincipalIssuable_2e953de7-c944-47a7-ae75-622cf3e36825" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromConvertibleDebt_0d809add-062c-4ee6-afcd-82092f1a4a8a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_ProceedsFromConvertibleDebt_0d809add-062c-4ee6-afcd-82092f1a4a8a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_b7e0ea31-9e92-48fc-af75-d52c96169641" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_b7e0ea31-9e92-48fc-af75-d52c96169641" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_772bb943-f214-40c1-9da4-581a51cd3d64" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_772bb943-f214-40c1-9da4-581a51cd3d64" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_4ac1f4e4-5ef1-4367-a210-ad630e2a0f7a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionRatio1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_4ac1f4e4-5ef1-4367-a210-ad630e2a0f7a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_1b7102ed-27fd-4fee-aa0e-3c3038679e50" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_1b7102ed-27fd-4fee-aa0e-3c3038679e50" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_40417a55-0702-46d7-aa6a-64caf2b9077c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_40417a55-0702-46d7-aa6a-64caf2b9077c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_4c45f38a-cfdf-4f73-aac2-909d96ce2df2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_4c45f38a-cfdf-4f73-aac2-909d96ce2df2" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_16738691-ea8e-4453-986a-712e1e526d73" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_16738691-ea8e-4453-986a-712e1e526d73" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_4d508b27-0970-4608-8487-253a10febc44" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_4d508b27-0970-4608-8487-253a10febc44" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionConvertedInstrumentAmount1_2b7e5df3-2a67-4316-88b6-4a0707cc0b93" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtConversionConvertedInstrumentAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtConversionConvertedInstrumentAmount1_2b7e5df3-2a67-4316-88b6-4a0707cc0b93" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionConvertedInstrumentSharesIssued1_4cac8ddb-29c2-4869-b43b-7d8ee0ff63b3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtConversionConvertedInstrumentSharesIssued1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtConversionConvertedInstrumentSharesIssued1_4cac8ddb-29c2-4869-b43b-7d8ee0ff63b3" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRepurchasedFaceAmount_f4e78dc4-4376-4241-9585-176a7ec4960e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRepurchasedFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentRepurchasedFaceAmount_f4e78dc4-4376-4241-9585-176a7ec4960e" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfConvertibleDebt_cce7b785-5bc6-4d87-ade4-8af0c3dcc98a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RepaymentsOfConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_RepaymentsOfConvertibleDebt_cce7b785-5bc6-4d87-ade4-8af0c3dcc98a" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_38ece7a3-a8f5-43b1-a815-df56a060f710" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_38ece7a3-a8f5-43b1-a815-df56a060f710" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFairValue_89bffe62-a145-440a-9bda-47741303540f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentFairValue_89bffe62-a145-440a-9bda-47741303540f" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_05cdf2b1-a471-40a5-97f4-4f30a6bba883" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_LongTermDebt_05cdf2b1-a471-40a5-97f4-4f30a6bba883" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_25c2a822-833c-452e-96c1-101089383708" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_25c2a822-833c-452e-96c1-101089383708" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_DebtInstrumentConvertibleCarryingAmountOfEquityComponentGross_9b5b184d-9818-44ec-bac2-82fb85241893" xlink:href="cloud-20220331.xsd#cloud_DebtInstrumentConvertibleCarryingAmountOfEquityComponentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_cloud_DebtInstrumentConvertibleCarryingAmountOfEquityComponentGross_9b5b184d-9818-44ec-bac2-82fb85241893" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharePrice_190050c2-1a40-4851-ade9-0d945222e425" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_SharePrice_190050c2-1a40-4851-ade9-0d945222e425" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleIfConvertedValueInExcessOfPrincipal_f88e085b-5a02-4fbd-b446-639000a1e389" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleIfConvertedValueInExcessOfPrincipal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentConvertibleIfConvertedValueInExcessOfPrincipal_f88e085b-5a02-4fbd-b446-639000a1e389" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1_19a2bbec-1beb-42dc-9018-ecf052dd331e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1_19a2bbec-1beb-42dc-9018-ecf052dd331e" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_1fa189a0-2383-4cbe-86d3-85fc235877cf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33a6f0ab-82ad-4562-8143-d8f0761a97ed" xlink:to="loc_us-gaap_DebtInstrumentTable_1fa189a0-2383-4cbe-86d3-85fc235877cf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_70989180-1d53-4728-941d-790745a894d7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1fa189a0-2383-4cbe-86d3-85fc235877cf" xlink:to="loc_us-gaap_DebtInstrumentAxis_70989180-1d53-4728-941d-790745a894d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_70989180-1d53-4728-941d-790745a894d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_70989180-1d53-4728-941d-790745a894d7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_70989180-1d53-4728-941d-790745a894d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ed1ce93e-449d-4021-83fd-bf430c345341" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_70989180-1d53-4728-941d-790745a894d7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ed1ce93e-449d-4021-83fd-bf430c345341" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2025Member_c2864dc7-ad47-4ea0-8c94-88c03ba1114c" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ed1ce93e-449d-4021-83fd-bf430c345341" xlink:to="loc_cloud_SeniorConvertibleNotesDue2025Member_c2864dc7-ad47-4ea0-8c94-88c03ba1114c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_43e0eb8b-2c3c-4b45-9a91-a2e6b3af7ffe" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1fa189a0-2383-4cbe-86d3-85fc235877cf" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_43e0eb8b-2c3c-4b45-9a91-a2e6b3af7ffe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_43e0eb8b-2c3c-4b45-9a91-a2e6b3af7ffe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_43e0eb8b-2c3c-4b45-9a91-a2e6b3af7ffe" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_43e0eb8b-2c3c-4b45-9a91-a2e6b3af7ffe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2158e4fd-e673-4b76-b334-0836c87abb8c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_43e0eb8b-2c3c-4b45-9a91-a2e6b3af7ffe" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2158e4fd-e673-4b76-b334-0836c87abb8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_64ed47fb-308b-424c-bca1-1bdb346f473b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2158e4fd-e673-4b76-b334-0836c87abb8c" xlink:to="loc_us-gaap_ConvertibleDebtMember_64ed47fb-308b-424c-bca1-1bdb346f473b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionByUniqueDescriptionAxis_ac103e22-89a8-457d-b7ee-9ec9104b74b5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtConversionByUniqueDescriptionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1fa189a0-2383-4cbe-86d3-85fc235877cf" xlink:to="loc_us-gaap_DebtConversionByUniqueDescriptionAxis_ac103e22-89a8-457d-b7ee-9ec9104b74b5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionNameDomain_ac103e22-89a8-457d-b7ee-9ec9104b74b5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtConversionNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtConversionByUniqueDescriptionAxis_ac103e22-89a8-457d-b7ee-9ec9104b74b5" xlink:to="loc_us-gaap_DebtConversionNameDomain_ac103e22-89a8-457d-b7ee-9ec9104b74b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionNameDomain_48cd5bd6-c0cc-4d5b-a52b-501d06f98ac8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtConversionNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtConversionByUniqueDescriptionAxis_ac103e22-89a8-457d-b7ee-9ec9104b74b5" xlink:to="loc_us-gaap_DebtConversionNameDomain_48cd5bd6-c0cc-4d5b-a52b-501d06f98ac8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ScenarioOneMember_b8f0f1ec-80ed-497c-8876-d2ab0a2729cf" xlink:href="cloud-20220331.xsd#cloud_ScenarioOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtConversionNameDomain_48cd5bd6-c0cc-4d5b-a52b-501d06f98ac8" xlink:to="loc_cloud_ScenarioOneMember_b8f0f1ec-80ed-497c-8876-d2ab0a2729cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ScenarioTwoMember_38eceab3-15d4-4cdf-a517-ccd0d1ee68b7" xlink:href="cloud-20220331.xsd#cloud_ScenarioTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtConversionNameDomain_48cd5bd6-c0cc-4d5b-a52b-501d06f98ac8" xlink:to="loc_cloud_ScenarioTwoMember_38eceab3-15d4-4cdf-a517-ccd0d1ee68b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ExchangeEventAxis_3d5dc960-885f-4990-9290-585614b0d9f1" xlink:href="cloud-20220331.xsd#cloud_ExchangeEventAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1fa189a0-2383-4cbe-86d3-85fc235877cf" xlink:to="loc_cloud_ExchangeEventAxis_3d5dc960-885f-4990-9290-585614b0d9f1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ExchangeEventDomain_3d5dc960-885f-4990-9290-585614b0d9f1_default" xlink:href="cloud-20220331.xsd#cloud_ExchangeEventDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_cloud_ExchangeEventAxis_3d5dc960-885f-4990-9290-585614b0d9f1" xlink:to="loc_cloud_ExchangeEventDomain_3d5dc960-885f-4990-9290-585614b0d9f1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ExchangeEventDomain_02f3cd09-00dd-4b25-b9c6-c78656f86ab5" xlink:href="cloud-20220331.xsd#cloud_ExchangeEventDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_cloud_ExchangeEventAxis_3d5dc960-885f-4990-9290-585614b0d9f1" xlink:to="loc_cloud_ExchangeEventDomain_02f3cd09-00dd-4b25-b9c6-c78656f86ab5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CertainHoldersConversionMember_a502e63e-0e65-4c94-b5ac-b53e295fc408" xlink:href="cloud-20220331.xsd#cloud_CertainHoldersConversionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cloud_ExchangeEventDomain_02f3cd09-00dd-4b25-b9c6-c78656f86ab5" xlink:to="loc_cloud_CertainHoldersConversionMember_a502e63e-0e65-4c94-b5ac-b53e295fc408" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_a1eb4e75-9820-45d2-a728-52cb6cd4cdb6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1fa189a0-2383-4cbe-86d3-85fc235877cf" xlink:to="loc_us-gaap_StatementClassOfStockAxis_a1eb4e75-9820-45d2-a728-52cb6cd4cdb6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_a1eb4e75-9820-45d2-a728-52cb6cd4cdb6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_a1eb4e75-9820-45d2-a728-52cb6cd4cdb6" xlink:to="loc_us-gaap_ClassOfStockDomain_a1eb4e75-9820-45d2-a728-52cb6cd4cdb6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_9f3599f0-f0bd-479c-8d43-df7e44856e3a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_a1eb4e75-9820-45d2-a728-52cb6cd4cdb6" xlink:to="loc_us-gaap_ClassOfStockDomain_9f3599f0-f0bd-479c-8d43-df7e44856e3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_4b52695b-a200-40ed-8d99-2f86f9b87fb0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_9f3599f0-f0bd-479c-8d43-df7e44856e3a" xlink:to="loc_us-gaap_CommonClassAMember_4b52695b-a200-40ed-8d99-2f86f9b87fb0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/Debt2025CappedCallTransactionsDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#Debt2025CappedCallTransactionsDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/Debt2025CappedCallTransactionsDetails" xlink:type="extended" id="i2be9f1d6393f4acab532ff150473b71b_Debt2025CappedCallTransactionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_1306560b-a575-4775-a48d-07c33ed07c3e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionIndexedToIssuersEquityStrikePrice1_f52920f2-fbf1-4e78-9f88-38e1ce99e27c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OptionIndexedToIssuersEquityStrikePrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1306560b-a575-4775-a48d-07c33ed07c3e" xlink:to="loc_us-gaap_OptionIndexedToIssuersEquityStrikePrice1_f52920f2-fbf1-4e78-9f88-38e1ce99e27c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CappedCallInitialCapPrice_fad8a7de-746c-4056-b4bf-daa615123e68" xlink:href="cloud-20220331.xsd#cloud_CappedCallInitialCapPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1306560b-a575-4775-a48d-07c33ed07c3e" xlink:to="loc_cloud_CappedCallInitialCapPrice_fad8a7de-746c-4056-b4bf-daa615123e68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SharesCoveredByCappedCalls_3de8ba03-4a63-476d-8904-1a912558e48e" xlink:href="cloud-20220331.xsd#cloud_SharesCoveredByCappedCalls"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1306560b-a575-4775-a48d-07c33ed07c3e" xlink:to="loc_cloud_SharesCoveredByCappedCalls_3de8ba03-4a63-476d-8904-1a912558e48e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_AdjustmentsToAdditionalPaidInCapitalPurchasesOfCappedCallsRelatedToConvertibleDebt_d96cb23d-a4a2-4813-850a-18b89b4f02c2" xlink:href="cloud-20220331.xsd#cloud_AdjustmentsToAdditionalPaidInCapitalPurchasesOfCappedCallsRelatedToConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1306560b-a575-4775-a48d-07c33ed07c3e" xlink:to="loc_cloud_AdjustmentsToAdditionalPaidInCapitalPurchasesOfCappedCallsRelatedToConvertibleDebt_d96cb23d-a4a2-4813-850a-18b89b4f02c2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_9f82d230-4658-463d-8cb8-4ec88e85e7fb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1306560b-a575-4775-a48d-07c33ed07c3e" xlink:to="loc_us-gaap_DebtInstrumentTable_9f82d230-4658-463d-8cb8-4ec88e85e7fb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_a1654fd5-3909-4fdc-bff1-5767c6d05472" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_9f82d230-4658-463d-8cb8-4ec88e85e7fb" xlink:to="loc_us-gaap_DebtInstrumentAxis_a1654fd5-3909-4fdc-bff1-5767c6d05472" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_a1654fd5-3909-4fdc-bff1-5767c6d05472_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_a1654fd5-3909-4fdc-bff1-5767c6d05472" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_a1654fd5-3909-4fdc-bff1-5767c6d05472_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_f2511f52-9ce0-4953-b472-b704daa50e54" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_a1654fd5-3909-4fdc-bff1-5767c6d05472" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_f2511f52-9ce0-4953-b472-b704daa50e54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2025Member_98f8d419-ed8e-424c-b132-f4edfdd0df81" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_f2511f52-9ce0-4953-b472-b704daa50e54" xlink:to="loc_cloud_SeniorConvertibleNotesDue2025Member_98f8d419-ed8e-424c-b132-f4edfdd0df81" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_d7e7a95e-ba85-44c5-8ea6-bbf0c4c4bb07" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_9f82d230-4658-463d-8cb8-4ec88e85e7fb" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_d7e7a95e-ba85-44c5-8ea6-bbf0c4c4bb07" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_d7e7a95e-ba85-44c5-8ea6-bbf0c4c4bb07_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_d7e7a95e-ba85-44c5-8ea6-bbf0c4c4bb07" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_d7e7a95e-ba85-44c5-8ea6-bbf0c4c4bb07_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_1d31a99a-b6bf-46b9-8bd0-4a5233461717" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_d7e7a95e-ba85-44c5-8ea6-bbf0c4c4bb07" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_1d31a99a-b6bf-46b9-8bd0-4a5233461717" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CappedCallsMember_64c97e49-6484-4953-a790-1d4e836a944a" xlink:href="cloud-20220331.xsd#cloud_CappedCallsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_1d31a99a-b6bf-46b9-8bd0-4a5233461717" xlink:to="loc_cloud_CappedCallsMember_64c97e49-6484-4953-a790-1d4e836a944a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_d205fffb-cff8-4d57-9213-782f001d00d0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_9f82d230-4658-463d-8cb8-4ec88e85e7fb" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_d205fffb-cff8-4d57-9213-782f001d00d0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_d205fffb-cff8-4d57-9213-782f001d00d0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_d205fffb-cff8-4d57-9213-782f001d00d0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_d205fffb-cff8-4d57-9213-782f001d00d0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_71c57bc9-84b1-4373-a7c8-4e95b3f8af60" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_d205fffb-cff8-4d57-9213-782f001d00d0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_71c57bc9-84b1-4373-a7c8-4e95b3f8af60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_8fbd8146-6b30-4743-a6ee-231d424e9b1c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_71c57bc9-84b1-4373-a7c8-4e95b3f8af60" xlink:to="loc_us-gaap_ConvertibleDebtMember_8fbd8146-6b30-4743-a6ee-231d424e9b1c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionAxis_f64ac7d2-b099-4574-a6da-39b103cd697b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PositionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_9f82d230-4658-463d-8cb8-4ec88e85e7fb" xlink:to="loc_us-gaap_PositionAxis_f64ac7d2-b099-4574-a6da-39b103cd697b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionDomain_f64ac7d2-b099-4574-a6da-39b103cd697b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PositionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PositionAxis_f64ac7d2-b099-4574-a6da-39b103cd697b" xlink:to="loc_us-gaap_PositionDomain_f64ac7d2-b099-4574-a6da-39b103cd697b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionDomain_88a263c4-a29b-41b1-ab8c-cdfb625609c3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PositionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PositionAxis_f64ac7d2-b099-4574-a6da-39b103cd697b" xlink:to="loc_us-gaap_PositionDomain_88a263c4-a29b-41b1-ab8c-cdfb625609c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongMember_bebc6c54-0f5c-4df3-b678-87e5ce6cc699" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PositionDomain_88a263c4-a29b-41b1-ab8c-cdfb625609c3" xlink:to="loc_us-gaap_LongMember_bebc6c54-0f5c-4df3-b678-87e5ce6cc699" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_be344ca0-4fa6-4d33-b4e6-7c2af0e5d506" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_9f82d230-4658-463d-8cb8-4ec88e85e7fb" xlink:to="loc_us-gaap_StatementClassOfStockAxis_be344ca0-4fa6-4d33-b4e6-7c2af0e5d506" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_be344ca0-4fa6-4d33-b4e6-7c2af0e5d506_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_be344ca0-4fa6-4d33-b4e6-7c2af0e5d506" xlink:to="loc_us-gaap_ClassOfStockDomain_be344ca0-4fa6-4d33-b4e6-7c2af0e5d506_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_632977c9-4b0b-4e87-8d78-a70adb553591" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_be344ca0-4fa6-4d33-b4e6-7c2af0e5d506" xlink:to="loc_us-gaap_ClassOfStockDomain_632977c9-4b0b-4e87-8d78-a70adb553591" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_acb1fec7-0375-44b5-ae8c-dd21c16c7dbd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_632977c9-4b0b-4e87-8d78-a70adb553591" xlink:to="loc_us-gaap_CommonClassAMember_acb1fec7-0375-44b5-ae8c-dd21c16c7dbd" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/DebtScheduleofNetCarryingAmountofNotesDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#DebtScheduleofNetCarryingAmountofNotesDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/DebtScheduleofNetCarryingAmountofNotesDetails" xlink:type="extended" id="i5bf05250f00f423b9bb181a1456e7930_DebtScheduleofNetCarryingAmountofNotesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_53f01ee0-1bd8-4e6f-a9a4-959034db0f18" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_3a650d4b-8e15-47a4-b7de-ca3333154a71" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_53f01ee0-1bd8-4e6f-a9a4-959034db0f18" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_3a650d4b-8e15-47a4-b7de-ca3333154a71" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_079530a2-0c00-40d0-89a3-5c655a817dea" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_53f01ee0-1bd8-4e6f-a9a4-959034db0f18" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscount_079530a2-0c00-40d0-89a3-5c655a817dea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_9d1678c9-4352-4ebd-8081-3dcbdf5d5d05" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_UnamortizedDebtIssuanceExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_53f01ee0-1bd8-4e6f-a9a4-959034db0f18" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_9d1678c9-4352-4ebd-8081-3dcbdf5d5d05" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_9f802f05-b791-4bb3-826e-a018dfa56e8c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_53f01ee0-1bd8-4e6f-a9a4-959034db0f18" xlink:to="loc_us-gaap_LongTermDebt_9f802f05-b791-4bb3-826e-a018dfa56e8c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_8ce3a3a3-3b38-4e23-8642-c04a273f850a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_53f01ee0-1bd8-4e6f-a9a4-959034db0f18" xlink:to="loc_us-gaap_DebtInstrumentTable_8ce3a3a3-3b38-4e23-8642-c04a273f850a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_321fe8d1-2746-4c5d-94da-8ff90f127a2b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8ce3a3a3-3b38-4e23-8642-c04a273f850a" xlink:to="loc_us-gaap_DebtInstrumentAxis_321fe8d1-2746-4c5d-94da-8ff90f127a2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_321fe8d1-2746-4c5d-94da-8ff90f127a2b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_321fe8d1-2746-4c5d-94da-8ff90f127a2b" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_321fe8d1-2746-4c5d-94da-8ff90f127a2b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_22df2cd0-3176-4948-b6fd-1a9b11a1a0f8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_321fe8d1-2746-4c5d-94da-8ff90f127a2b" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_22df2cd0-3176-4948-b6fd-1a9b11a1a0f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2026Member_24c510b1-5fe8-4d22-8e81-9863a0ea03a0" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22df2cd0-3176-4948-b6fd-1a9b11a1a0f8" xlink:to="loc_cloud_SeniorConvertibleNotesDue2026Member_24c510b1-5fe8-4d22-8e81-9863a0ea03a0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2025Member_71f54037-8667-4409-991f-b0b3a5220a8c" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_22df2cd0-3176-4948-b6fd-1a9b11a1a0f8" xlink:to="loc_cloud_SeniorConvertibleNotesDue2025Member_71f54037-8667-4409-991f-b0b3a5220a8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_913f401a-b38f-4c30-8c96-392eaa497695" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8ce3a3a3-3b38-4e23-8642-c04a273f850a" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_913f401a-b38f-4c30-8c96-392eaa497695" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_913f401a-b38f-4c30-8c96-392eaa497695_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_913f401a-b38f-4c30-8c96-392eaa497695" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_913f401a-b38f-4c30-8c96-392eaa497695_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_9c9d1420-4275-4f3c-91a7-6bbd4981badb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_913f401a-b38f-4c30-8c96-392eaa497695" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_9c9d1420-4275-4f3c-91a7-6bbd4981badb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_de2f12b1-22ca-4fe6-a996-383aef7723f9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_9c9d1420-4275-4f3c-91a7-6bbd4981badb" xlink:to="loc_us-gaap_ConvertibleDebtMember_de2f12b1-22ca-4fe6-a996-383aef7723f9" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/DebtScheduleofInterestComponentsDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#DebtScheduleofInterestComponentsDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/DebtScheduleofInterestComponentsDetails" xlink:type="extended" id="i98c6c7c84aa445798aedcc2cee3a31ec_DebtScheduleofInterestComponentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_b5d2e82a-b7c8-4a12-9f34-b07d75e06e57" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_2828637b-8d71-41bc-930e-e0c72c6bdf3a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b5d2e82a-b7c8-4a12-9f34-b07d75e06e57" xlink:to="loc_us-gaap_InterestExpenseDebt_2828637b-8d71-41bc-930e-e0c72c6bdf3a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfDebtDiscountPremium_237f6fa6-8ce9-4057-993d-23f7cfed7ba7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AmortizationOfDebtDiscountPremium"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b5d2e82a-b7c8-4a12-9f34-b07d75e06e57" xlink:to="loc_us-gaap_AmortizationOfDebtDiscountPremium_237f6fa6-8ce9-4057-993d-23f7cfed7ba7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_bdc30d24-a06b-4e52-907f-73495384d36b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b5d2e82a-b7c8-4a12-9f34-b07d75e06e57" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_bdc30d24-a06b-4e52-907f-73495384d36b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestAndDebtExpense_9d7049f4-7ae5-4550-b317-a06b3cc3bd5f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestAndDebtExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b5d2e82a-b7c8-4a12-9f34-b07d75e06e57" xlink:to="loc_us-gaap_InterestAndDebtExpense_9d7049f4-7ae5-4550-b317-a06b3cc3bd5f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_cdd1d66a-6538-4e20-861b-e6902ae1ab45" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b5d2e82a-b7c8-4a12-9f34-b07d75e06e57" xlink:to="loc_us-gaap_DebtInstrumentTable_cdd1d66a-6538-4e20-861b-e6902ae1ab45" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_b033ccc4-fa68-4de1-bc50-1d9f0d5e236e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_cdd1d66a-6538-4e20-861b-e6902ae1ab45" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_b033ccc4-fa68-4de1-bc50-1d9f0d5e236e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_b033ccc4-fa68-4de1-bc50-1d9f0d5e236e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_b033ccc4-fa68-4de1-bc50-1d9f0d5e236e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_b033ccc4-fa68-4de1-bc50-1d9f0d5e236e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_5be5d8dd-e445-413a-9eb9-2944c9eb58d5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_b033ccc4-fa68-4de1-bc50-1d9f0d5e236e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_5be5d8dd-e445-413a-9eb9-2944c9eb58d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_69a89f5a-2e21-4ba6-be70-7e9d93e4daa9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_5be5d8dd-e445-413a-9eb9-2944c9eb58d5" xlink:to="loc_us-gaap_ConvertibleDebtMember_69a89f5a-2e21-4ba6-be70-7e9d93e4daa9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_55ffea21-656b-4d4d-8bed-5360ab3153a3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_cdd1d66a-6538-4e20-861b-e6902ae1ab45" xlink:to="loc_us-gaap_DebtInstrumentAxis_55ffea21-656b-4d4d-8bed-5360ab3153a3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_55ffea21-656b-4d4d-8bed-5360ab3153a3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_55ffea21-656b-4d4d-8bed-5360ab3153a3" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_55ffea21-656b-4d4d-8bed-5360ab3153a3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1a7b4805-a03a-4a2e-a22f-07ffad73c703" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_55ffea21-656b-4d4d-8bed-5360ab3153a3" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1a7b4805-a03a-4a2e-a22f-07ffad73c703" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2026Member_d470b26d-619e-4477-ba6b-8844d41d406f" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1a7b4805-a03a-4a2e-a22f-07ffad73c703" xlink:to="loc_cloud_SeniorConvertibleNotesDue2026Member_d470b26d-619e-4477-ba6b-8844d41d406f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2025Member_6ded27f2-2188-4580-ac11-7a887de7d20e" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1a7b4805-a03a-4a2e-a22f-07ffad73c703" xlink:to="loc_cloud_SeniorConvertibleNotesDue2025Member_6ded27f2-2188-4580-ac11-7a887de7d20e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/CommonStockNarrativesDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#CommonStockNarrativesDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/CommonStockNarrativesDetails" xlink:type="extended" id="i169ce107b9ce46fb9cf4ab3d2718a871_CommonStockNarrativesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_c59b82e3-ad4e-4b37-a1fd-00dab9aee05f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_CommonStockVotingRightsNumberOfVotesForEachShare_fdec740d-e5e9-4441-8be2-c1a0ec7811f9" xlink:href="cloud-20220331.xsd#cloud_CommonStockVotingRightsNumberOfVotesForEachShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_c59b82e3-ad4e-4b37-a1fd-00dab9aee05f" xlink:to="loc_cloud_CommonStockVotingRightsNumberOfVotesForEachShare_fdec740d-e5e9-4441-8be2-c1a0ec7811f9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_72c297a3-f990-4978-b92f-35d3c6f03bd7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_c59b82e3-ad4e-4b37-a1fd-00dab9aee05f" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_72c297a3-f990-4978-b92f-35d3c6f03bd7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_ef88bf23-a09c-4773-b0d4-ea0825df757c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_c59b82e3-ad4e-4b37-a1fd-00dab9aee05f" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_ef88bf23-a09c-4773-b0d4-ea0825df757c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_99b765d0-2428-424c-bc98-5b1c87a52e41" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_c59b82e3-ad4e-4b37-a1fd-00dab9aee05f" xlink:to="loc_us-gaap_CommonStockSharesIssued_99b765d0-2428-424c-bc98-5b1c87a52e41" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_c1ab401a-07bd-4b11-b69c-32d8d9bb7824" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_c59b82e3-ad4e-4b37-a1fd-00dab9aee05f" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_c1ab401a-07bd-4b11-b69c-32d8d9bb7824" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_8936f553-f055-439a-99e2-b1958601cfde" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_c59b82e3-ad4e-4b37-a1fd-00dab9aee05f" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_8936f553-f055-439a-99e2-b1958601cfde" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_63531067-7bcf-41b3-aa5e-8d0a57b864b2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_8936f553-f055-439a-99e2-b1958601cfde" xlink:to="loc_us-gaap_StatementClassOfStockAxis_63531067-7bcf-41b3-aa5e-8d0a57b864b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_63531067-7bcf-41b3-aa5e-8d0a57b864b2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_63531067-7bcf-41b3-aa5e-8d0a57b864b2" xlink:to="loc_us-gaap_ClassOfStockDomain_63531067-7bcf-41b3-aa5e-8d0a57b864b2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_edd11c97-9bec-45f4-8f51-edcbc8d70a50" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_63531067-7bcf-41b3-aa5e-8d0a57b864b2" xlink:to="loc_us-gaap_ClassOfStockDomain_edd11c97-9bec-45f4-8f51-edcbc8d70a50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_4735c4be-d1c2-4a52-aff0-035bbb96d861" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_edd11c97-9bec-45f4-8f51-edcbc8d70a50" xlink:to="loc_us-gaap_CommonClassAMember_4735c4be-d1c2-4a52-aff0-035bbb96d861" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_7f6d532f-0163-48f8-927b-1abffcdd03fb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_edd11c97-9bec-45f4-8f51-edcbc8d70a50" xlink:to="loc_us-gaap_CommonClassBMember_7f6d532f-0163-48f8-927b-1abffcdd03fb" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/CommonStockScheduleofCommonStockReservedforFutureIssuanceDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#CommonStockScheduleofCommonStockReservedforFutureIssuanceDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/CommonStockScheduleofCommonStockReservedforFutureIssuanceDetails" xlink:type="extended" id="ifc14625f7b274fe9a63ff44ed83b9f3e_CommonStockScheduleofCommonStockReservedforFutureIssuanceDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_65bbc275-4301-4e1c-bf23-926718e453b9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_59c96929-a7c4-46be-9a8d-452866e6b40a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_65bbc275-4301-4e1c-bf23-926718e453b9" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_59c96929-a7c4-46be-9a8d-452866e6b40a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_ce09ca29-9f44-4331-95fd-7a7e842f66a7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_65bbc275-4301-4e1c-bf23-926718e453b9" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_ce09ca29-9f44-4331-95fd-7a7e842f66a7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_05193c8b-f67f-4b7d-a1db-07667e2f3879" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_ce09ca29-9f44-4331-95fd-7a7e842f66a7" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_05193c8b-f67f-4b7d-a1db-07667e2f3879" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_05193c8b-f67f-4b7d-a1db-07667e2f3879_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_05193c8b-f67f-4b7d-a1db-07667e2f3879" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_05193c8b-f67f-4b7d-a1db-07667e2f3879_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_0a26530d-5d44-4374-b711-78591e640850" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_05193c8b-f67f-4b7d-a1db-07667e2f3879" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_0a26530d-5d44-4374-b711-78591e640850" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_80de5dac-6c3e-42f7-a779-592963465bf4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_0a26530d-5d44-4374-b711-78591e640850" xlink:to="loc_us-gaap_ConvertibleDebtMember_80de5dac-6c3e-42f7-a779-592963465bf4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_ecf69293-efe9-4408-94b6-5781ec913440" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_ce09ca29-9f44-4331-95fd-7a7e842f66a7" xlink:to="loc_us-gaap_AwardTypeAxis_ecf69293-efe9-4408-94b6-5781ec913440" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ecf69293-efe9-4408-94b6-5781ec913440_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_ecf69293-efe9-4408-94b6-5781ec913440" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ecf69293-efe9-4408-94b6-5781ec913440_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_98ee6534-9770-4a91-8922-09f7c1ee7df8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_ecf69293-efe9-4408-94b6-5781ec913440" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_98ee6534-9770-4a91-8922-09f7c1ee7df8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_be410477-f58e-49ec-91a1-5421b4e3c59d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_98ee6534-9770-4a91-8922-09f7c1ee7df8" xlink:to="loc_us-gaap_EmployeeStockOptionMember_be410477-f58e-49ec-91a1-5421b4e3c59d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_aa0aee0b-034a-4158-ba72-677be59714aa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_98ee6534-9770-4a91-8922-09f7c1ee7df8" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_aa0aee0b-034a-4158-ba72-677be59714aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_e524b190-0ef7-4f3c-bea4-fb56c8f0ffbc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_98ee6534-9770-4a91-8922-09f7c1ee7df8" xlink:to="loc_us-gaap_EmployeeStockMember_e524b190-0ef7-4f3c-bea4-fb56c8f0ffbc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_8ea556d6-1630-4f27-92d7-3c46ca743d8b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_ce09ca29-9f44-4331-95fd-7a7e842f66a7" xlink:to="loc_us-gaap_PlanNameAxis_8ea556d6-1630-4f27-92d7-3c46ca743d8b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_8ea556d6-1630-4f27-92d7-3c46ca743d8b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_8ea556d6-1630-4f27-92d7-3c46ca743d8b" xlink:to="loc_us-gaap_PlanNameDomain_8ea556d6-1630-4f27-92d7-3c46ca743d8b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_6808543d-0a77-44a5-86e6-2afe964f114b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_8ea556d6-1630-4f27-92d7-3c46ca743d8b" xlink:to="loc_us-gaap_PlanNameDomain_6808543d-0a77-44a5-86e6-2afe964f114b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_EquityIncentivePlan2019Member_d320df24-83f2-4319-9e68-bc3d5164265c" xlink:href="cloud-20220331.xsd#cloud_EquityIncentivePlan2019Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_6808543d-0a77-44a5-86e6-2afe964f114b" xlink:to="loc_cloud_EquityIncentivePlan2019Member_d320df24-83f2-4319-9e68-bc3d5164265c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_7c4aefff-2707-49bb-beae-0b9f40a2ac18" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_ce09ca29-9f44-4331-95fd-7a7e842f66a7" xlink:to="loc_us-gaap_DebtInstrumentAxis_7c4aefff-2707-49bb-beae-0b9f40a2ac18" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_7c4aefff-2707-49bb-beae-0b9f40a2ac18_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_7c4aefff-2707-49bb-beae-0b9f40a2ac18" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_7c4aefff-2707-49bb-beae-0b9f40a2ac18_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_54fece23-e800-419f-9bb9-9a50bf392c6d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_7c4aefff-2707-49bb-beae-0b9f40a2ac18" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_54fece23-e800-419f-9bb9-9a50bf392c6d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2025Member_395edadd-7a86-4ed9-93b1-3f5d4653d9d0" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_54fece23-e800-419f-9bb9-9a50bf392c6d" xlink:to="loc_cloud_SeniorConvertibleNotesDue2025Member_395edadd-7a86-4ed9-93b1-3f5d4653d9d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2026Member_440db863-4895-41cb-95af-4fcd4098ba96" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_54fece23-e800-419f-9bb9-9a50bf392c6d" xlink:to="loc_cloud_SeniorConvertibleNotesDue2026Member_440db863-4895-41cb-95af-4fcd4098ba96" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/StockbasedCompensationNarrativeDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#StockbasedCompensationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/StockbasedCompensationNarrativeDetails" xlink:type="extended" id="i3c24f756d79743a093892e337f2e8750_StockbasedCompensationNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardExercisePriceToFairMarketValuePercent_2833c9ff-a137-43d1-81a6-ef97fb7f3b69" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardExercisePriceToFairMarketValuePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardExercisePriceToFairMarketValuePercent_2833c9ff-a137-43d1-81a6-ef97fb7f3b69" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_8532a385-b705-439b-bdf0-5a3e8fa8b41c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_8532a385-b705-439b-bdf0-5a3e8fa8b41c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfNewSharesAuthorized_6867c595-756f-4df2-b6f0-1bc964c335b0" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfNewSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfNewSharesAuthorized_6867c595-756f-4df2-b6f0-1bc964c335b0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardRemainingNumberOfSharesAuthorized_0b6dde11-afb0-4529-86c9-c840f581a86c" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardRemainingNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardRemainingNumberOfSharesAuthorized_0b6dde11-afb0-4529-86c9-c840f581a86c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedPaymentAwardAnnualPercentageOfSharesAuthorized_d894e2e3-b7ba-4885-a72a-f46750de72d3" xlink:href="cloud-20220331.xsd#cloud_ShareBasedPaymentAwardAnnualPercentageOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_ShareBasedPaymentAwardAnnualPercentageOfSharesAuthorized_d894e2e3-b7ba-4885-a72a-f46750de72d3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedPaymentArrangementOptionNumberOfSharesReceivableUponExerciseOfStockOption_5328245a-732d-4fab-9c69-f93c8ba0ad42" xlink:href="cloud-20220331.xsd#cloud_ShareBasedPaymentArrangementOptionNumberOfSharesReceivableUponExerciseOfStockOption"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_ShareBasedPaymentArrangementOptionNumberOfSharesReceivableUponExerciseOfStockOption_5328245a-732d-4fab-9c69-f93c8ba0ad42" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_b73eb1e3-8a5d-41b8-ae70-1b6ad0e6b310" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_b73eb1e3-8a5d-41b8-ae70-1b6ad0e6b310" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_8a01f550-0983-4dcc-89f9-3e4d6c423e6b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_8a01f550-0983-4dcc-89f9-3e4d6c423e6b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_0fe227c0-fa8f-40e3-aaf3-2e0e33a30259" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_0fe227c0-fa8f-40e3-aaf3-2e0e33a30259" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsNonvestedExercisableNumber_4549b328-f668-4099-b51a-e2c7da8b15f4" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsNonvestedExercisableNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsNonvestedExercisableNumber_4549b328-f668-4099-b51a-e2c7da8b15f4" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_98b9116a-da95-40d8-935d-8ab864de3b42" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_98b9116a-da95-40d8-935d-8ab864de3b42" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_66564e35-2518-439e-8864-e07b0ae01bd3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_66564e35-2518-439e-8864-e07b0ae01bd3" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_a0aebbeb-ac30-47b0-be3e-26c7341cb40a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_a0aebbeb-ac30-47b0-be3e-26c7341cb40a" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_a2c236c4-5dca-41ce-828c-e5a6c87d9b4f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_a2c236c4-5dca-41ce-828c-e5a6c87d9b4f" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_0925727e-129a-43d2-a40e-62dcb7997058" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_0925727e-129a-43d2-a40e-62dcb7997058" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_05c03364-d0df-46f7-baaa-6bd0b900d221" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_05c03364-d0df-46f7-baaa-6bd0b900d221" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent_c53b0558-67d0-43fc-8758-8a410569fc0e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent_c53b0558-67d0-43fc-8758-8a410569fc0e" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationEstimatedQuantityOfSharesToBeRepurchasedInFollowingPeriod_324425d0-7df0-4765-9ef7-7030b8cc2549" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationEstimatedQuantityOfSharesToBeRepurchasedInFollowingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationEstimatedQuantityOfSharesToBeRepurchasedInFollowingPeriod_324425d0-7df0-4765-9ef7-7030b8cc2549" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_cf661191-0e1b-4a59-98d0-2ffa4cf73b1b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_cf661191-0e1b-4a59-98d0-2ffa4cf73b1b" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_59462bd3-c95f-46c2-a833-6752cbfa4a73" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_59462bd3-c95f-46c2-a833-6752cbfa4a73" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_8a909f29-12bf-4e5b-ac29-37916412155d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_8a909f29-12bf-4e5b-ac29-37916412155d" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_IssuanceOfUnvestedRestrictedStockInConnectionWithAcquisitionShares_5a91ecdb-1eb9-4134-9e5a-1784ecf4cdf9" xlink:href="cloud-20220331.xsd#cloud_IssuanceOfUnvestedRestrictedStockInConnectionWithAcquisitionShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_IssuanceOfUnvestedRestrictedStockInConnectionWithAcquisitionShares_5a91ecdb-1eb9-4134-9e5a-1784ecf4cdf9" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_979861f7-8b82-45d8-bdf7-6064517a21e9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_979861f7-8b82-45d8-bdf7-6064517a21e9" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_RestrictedStockIssuedInConnectionWithAcquisitionAggregateGrantDateFairValue_833cf84a-4ecc-41a3-a2a1-26534c4fb253" xlink:href="cloud-20220331.xsd#cloud_RestrictedStockIssuedInConnectionWithAcquisitionAggregateGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_RestrictedStockIssuedInConnectionWithAcquisitionAggregateGrantDateFairValue_833cf84a-4ecc-41a3-a2a1-26534c4fb253" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_52023b39-02ae-48e7-b70c-855fd4efbb20" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_52023b39-02ae-48e7-b70c-855fd4efbb20" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAllowableUnderThePlan_7178e013-c869-4255-96d6-b124de89816e" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAllowableUnderThePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAllowableUnderThePlan_7178e013-c869-4255-96d6-b124de89816e" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum_6c874156-d64b-4d8d-8841-42ee74027d7a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum_6c874156-d64b-4d8d-8841-42ee74027d7a" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumOwnershipPercentageThresholdForParticipation_87ad3602-ed6d-435b-a772-9af16fcf6757" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumOwnershipPercentageThresholdForParticipation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumOwnershipPercentageThresholdForParticipation_87ad3602-ed6d-435b-a772-9af16fcf6757" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumContributionPerEmployeePercent_d43ae4fd-4de8-473a-9040-3f9eb902b6bc" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumContributionPerEmployeePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumContributionPerEmployeePercent_d43ae4fd-4de8-473a-9040-3f9eb902b6bc" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_6c3068f9-78fa-423e-967c-ea6c5dabfcde" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_6c3068f9-78fa-423e-967c-ea6c5dabfcde" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod_0a376b75-4665-462b-8e59-dd88b266eb67" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod_0a376b75-4665-462b-8e59-dd88b266eb67" xlink:type="arc" order="30"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePeriod_ccaefebd-5449-4e63-8382-9ec8053b75c8" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePeriod_ccaefebd-5449-4e63-8382-9ec8053b75c8" xlink:type="arc" order="31"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee_1b765a6b-fa34-4354-b9fb-729f9917fc17" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee_1b765a6b-fa34-4354-b9fb-729f9917fc17" xlink:type="arc" order="32"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionAmount_2ccc2d3f-0044-4d4a-8c02-26f72332ee8d" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionAmount_2ccc2d3f-0044-4d4a-8c02-26f72332ee8d" xlink:type="arc" order="33"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05b809ad-c9b5-4ab0-b891-5313b1bc3e8f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_187b83c2-ac62-453e-804f-362588021134" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05b809ad-c9b5-4ab0-b891-5313b1bc3e8f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_502931b9-147a-41ee-8730-984cacc8085a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05b809ad-c9b5-4ab0-b891-5313b1bc3e8f" xlink:to="loc_us-gaap_AwardTypeAxis_502931b9-147a-41ee-8730-984cacc8085a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_502931b9-147a-41ee-8730-984cacc8085a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_502931b9-147a-41ee-8730-984cacc8085a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_502931b9-147a-41ee-8730-984cacc8085a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01139f20-684f-4755-9b5d-8956086f4f10" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_502931b9-147a-41ee-8730-984cacc8085a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01139f20-684f-4755-9b5d-8956086f4f10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_a2c180e3-d773-4ce7-9373-3605883f72c5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01139f20-684f-4755-9b5d-8956086f4f10" xlink:to="loc_us-gaap_EmployeeStockOptionMember_a2c180e3-d773-4ce7-9373-3605883f72c5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_2ebf8133-e692-4b8b-9a9b-d1322b7a0409" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01139f20-684f-4755-9b5d-8956086f4f10" xlink:to="loc_us-gaap_RestrictedStockMember_2ebf8133-e692-4b8b-9a9b-d1322b7a0409" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_66637744-1a9b-4a24-a400-ca21f8985bf4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01139f20-684f-4755-9b5d-8956086f4f10" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_66637744-1a9b-4a24-a400-ca21f8985bf4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_2de316c3-78db-4e56-bf8a-fd81d0879c3d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01139f20-684f-4755-9b5d-8956086f4f10" xlink:to="loc_us-gaap_EmployeeStockMember_2de316c3-78db-4e56-bf8a-fd81d0879c3d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_f64f23e3-40ce-48b9-84cc-6394377f33d4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05b809ad-c9b5-4ab0-b891-5313b1bc3e8f" xlink:to="loc_us-gaap_PlanNameAxis_f64f23e3-40ce-48b9-84cc-6394377f33d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_f64f23e3-40ce-48b9-84cc-6394377f33d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_f64f23e3-40ce-48b9-84cc-6394377f33d4" xlink:to="loc_us-gaap_PlanNameDomain_f64f23e3-40ce-48b9-84cc-6394377f33d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_685d7aeb-1ce6-4d32-9d80-62b5899a77cd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_f64f23e3-40ce-48b9-84cc-6394377f33d4" xlink:to="loc_us-gaap_PlanNameDomain_685d7aeb-1ce6-4d32-9d80-62b5899a77cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_TwoThousandAndTenEquityIncentivePlanMember_17b77631-3ba1-49da-8bf9-9f8d92f43b46" xlink:href="cloud-20220331.xsd#cloud_TwoThousandAndTenEquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_685d7aeb-1ce6-4d32-9d80-62b5899a77cd" xlink:to="loc_cloud_TwoThousandAndTenEquityIncentivePlanMember_17b77631-3ba1-49da-8bf9-9f8d92f43b46" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_TwoThousandAndNineteenEquityIncentivePlanMember_79355c5a-ffbb-44b2-b1ac-c27e1549ce43" xlink:href="cloud-20220331.xsd#cloud_TwoThousandAndNineteenEquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_685d7aeb-1ce6-4d32-9d80-62b5899a77cd" xlink:to="loc_cloud_TwoThousandAndNineteenEquityIncentivePlanMember_79355c5a-ffbb-44b2-b1ac-c27e1549ce43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_TwoThousandAndNineteenEmployeeStockPurchasePlanMember_da597499-f4b8-4cc0-a796-9c16e933945c" xlink:href="cloud-20220331.xsd#cloud_TwoThousandAndNineteenEmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_685d7aeb-1ce6-4d32-9d80-62b5899a77cd" xlink:to="loc_cloud_TwoThousandAndNineteenEmployeeStockPurchasePlanMember_da597499-f4b8-4cc0-a796-9c16e933945c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_3e5a0474-fcaa-461e-85ac-98e460a8df3a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05b809ad-c9b5-4ab0-b891-5313b1bc3e8f" xlink:to="loc_us-gaap_StatementClassOfStockAxis_3e5a0474-fcaa-461e-85ac-98e460a8df3a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_3e5a0474-fcaa-461e-85ac-98e460a8df3a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_3e5a0474-fcaa-461e-85ac-98e460a8df3a" xlink:to="loc_us-gaap_ClassOfStockDomain_3e5a0474-fcaa-461e-85ac-98e460a8df3a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_a0d6176e-7179-4d19-a98e-98c3b4b30845" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_3e5a0474-fcaa-461e-85ac-98e460a8df3a" xlink:to="loc_us-gaap_ClassOfStockDomain_a0d6176e-7179-4d19-a98e-98c3b4b30845" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_9ea914f3-20de-40bf-88be-3c4696f3c754" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_a0d6176e-7179-4d19-a98e-98c3b4b30845" xlink:to="loc_us-gaap_CommonStockMember_9ea914f3-20de-40bf-88be-3c4696f3c754" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_4d536e71-889a-493e-b8ea-fb6be4448525" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_a0d6176e-7179-4d19-a98e-98c3b4b30845" xlink:to="loc_us-gaap_CommonClassAMember_4d536e71-889a-493e-b8ea-fb6be4448525" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ClassAAndClassBCommonStockMember_800fe911-bf2b-42fc-b552-352607c998c1" xlink:href="cloud-20220331.xsd#cloud_ClassAAndClassBCommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_a0d6176e-7179-4d19-a98e-98c3b4b30845" xlink:to="loc_cloud_ClassAAndClassBCommonStockMember_800fe911-bf2b-42fc-b552-352607c998c1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_3b196dad-7c2b-4439-8df9-c6a62ad5c2f9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_a0d6176e-7179-4d19-a98e-98c3b4b30845" xlink:to="loc_us-gaap_CommonClassBMember_3b196dad-7c2b-4439-8df9-c6a62ad5c2f9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualAxis_897e507b-f501-43f8-87e6-4cf11b0f8f3a" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_TitleOfIndividualAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05b809ad-c9b5-4ab0-b891-5313b1bc3e8f" xlink:to="loc_srt_TitleOfIndividualAxis_897e507b-f501-43f8-87e6-4cf11b0f8f3a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_897e507b-f501-43f8-87e6-4cf11b0f8f3a_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_897e507b-f501-43f8-87e6-4cf11b0f8f3a" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_897e507b-f501-43f8-87e6-4cf11b0f8f3a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_b29dc8a2-ffcc-482b-bce6-7a02974c695d" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_897e507b-f501-43f8-87e6-4cf11b0f8f3a" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_b29dc8a2-ffcc-482b-bce6-7a02974c695d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ChiefExecutiveOfficerMember_54a24126-30c6-4cf6-b52f-6d331cf9c568" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ChiefExecutiveOfficerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_b29dc8a2-ffcc-482b-bce6-7a02974c695d" xlink:to="loc_srt_ChiefExecutiveOfficerMember_54a24126-30c6-4cf6-b52f-6d331cf9c568" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ChiefOperatingOfficerMember_ad38e103-92c6-49f0-8ac8-0c19b1bdcd6f" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ChiefOperatingOfficerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_b29dc8a2-ffcc-482b-bce6-7a02974c695d" xlink:to="loc_srt_ChiefOperatingOfficerMember_ad38e103-92c6-49f0-8ac8-0c19b1bdcd6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_PresidentMember_943359e0-6634-4190-95ca-95d770bee955" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_PresidentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_b29dc8a2-ffcc-482b-bce6-7a02974c695d" xlink:to="loc_srt_PresidentMember_943359e0-6634-4190-95ca-95d770bee955" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_127a98d6-02d1-4113-bdb0-8e6d7d4540c7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05b809ad-c9b5-4ab0-b891-5313b1bc3e8f" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_127a98d6-02d1-4113-bdb0-8e6d7d4540c7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_127a98d6-02d1-4113-bdb0-8e6d7d4540c7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_127a98d6-02d1-4113-bdb0-8e6d7d4540c7" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_127a98d6-02d1-4113-bdb0-8e6d7d4540c7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1aba6e5c-b5d8-4a21-a145-71b531862f51" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_127a98d6-02d1-4113-bdb0-8e6d7d4540c7" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1aba6e5c-b5d8-4a21-a145-71b531862f51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_VectrixIncMember_b1948d46-f435-404c-acdb-ad59ff0d2e31" xlink:href="cloud-20220331.xsd#cloud_VectrixIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1aba6e5c-b5d8-4a21-a145-71b531862f51" xlink:to="loc_cloud_VectrixIncMember_b1948d46-f435-404c-acdb-ad59ff0d2e31" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ZarazMember_0d883cd4-4cf2-4afd-8e84-c6a3d14950c5" xlink:href="cloud-20220331.xsd#cloud_ZarazMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1aba6e5c-b5d8-4a21-a145-71b531862f51" xlink:to="loc_cloud_ZarazMember_0d883cd4-4cf2-4afd-8e84-c6a3d14950c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_S2SystemsCorporationMember_6b2cbf04-8566-4b81-b379-3b6378c24764" xlink:href="cloud-20220331.xsd#cloud_S2SystemsCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1aba6e5c-b5d8-4a21-a145-71b531862f51" xlink:to="loc_cloud_S2SystemsCorporationMember_6b2cbf04-8566-4b81-b379-3b6378c24764" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_AdjustmentsToAdditionalPaidInCapitalPurchasesOfCappedCallsRelatedToConvertibleDebt_dbe3edce-b5b8-4aa3-8bb6-6664498c99f3" xlink:href="cloud-20220331.xsd#cloud_AdjustmentsToAdditionalPaidInCapitalPurchasesOfCappedCallsRelatedToConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1aba6e5c-b5d8-4a21-a145-71b531862f51" xlink:to="loc_cloud_AdjustmentsToAdditionalPaidInCapitalPurchasesOfCappedCallsRelatedToConvertibleDebt_dbe3edce-b5b8-4aa3-8bb6-6664498c99f3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_709c9c32-a0b7-42ce-9ac0-6f030c7409c3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05b809ad-c9b5-4ab0-b891-5313b1bc3e8f" xlink:to="loc_us-gaap_VestingAxis_709c9c32-a0b7-42ce-9ac0-6f030c7409c3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_709c9c32-a0b7-42ce-9ac0-6f030c7409c3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_709c9c32-a0b7-42ce-9ac0-6f030c7409c3" xlink:to="loc_us-gaap_VestingDomain_709c9c32-a0b7-42ce-9ac0-6f030c7409c3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_c0b56e0e-6405-4023-9e3a-c30d2adc2be0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_709c9c32-a0b7-42ce-9ac0-6f030c7409c3" xlink:to="loc_us-gaap_VestingDomain_c0b56e0e-6405-4023-9e3a-c30d2adc2be0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedPaymentArrangementSubjectToVestingMember_9ce1e825-0a93-48de-a9db-a7b07a75e372" xlink:href="cloud-20220331.xsd#cloud_ShareBasedPaymentArrangementSubjectToVestingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_c0b56e0e-6405-4023-9e3a-c30d2adc2be0" xlink:to="loc_cloud_ShareBasedPaymentArrangementSubjectToVestingMember_9ce1e825-0a93-48de-a9db-a7b07a75e372" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_e0ce3dde-2a44-422c-b721-2fcc51c8ec2f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationAwardTrancheOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_c0b56e0e-6405-4023-9e3a-c30d2adc2be0" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_e0ce3dde-2a44-422c-b721-2fcc51c8ec2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_2022abb4-bde0-4766-801f-39747154a681" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationAwardTrancheTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_c0b56e0e-6405-4023-9e3a-c30d2adc2be0" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_2022abb4-bde0-4766-801f-39747154a681" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_d2dea358-5bf9-4825-8c5d-83a3969659fc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationAwardTrancheThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_c0b56e0e-6405-4023-9e3a-c30d2adc2be0" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_d2dea358-5bf9-4825-8c5d-83a3969659fc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedPaymentArrangementTrancheFourMember_7950253b-803b-4340-b840-b46e415765ba" xlink:href="cloud-20220331.xsd#cloud_ShareBasedPaymentArrangementTrancheFourMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_c0b56e0e-6405-4023-9e3a-c30d2adc2be0" xlink:to="loc_cloud_ShareBasedPaymentArrangementTrancheFourMember_7950253b-803b-4340-b840-b46e415765ba" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedPaymentArrangementTrancheFiveMember_e8ef3da2-9e49-4ad1-b7da-66023484d4e6" xlink:href="cloud-20220331.xsd#cloud_ShareBasedPaymentArrangementTrancheFiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_c0b56e0e-6405-4023-9e3a-c30d2adc2be0" xlink:to="loc_cloud_ShareBasedPaymentArrangementTrancheFiveMember_e8ef3da2-9e49-4ad1-b7da-66023484d4e6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedPaymentArrangementTrancheSixMember_bd414e42-9d9f-49d0-822e-a835e212dd6f" xlink:href="cloud-20220331.xsd#cloud_ShareBasedPaymentArrangementTrancheSixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_c0b56e0e-6405-4023-9e3a-c30d2adc2be0" xlink:to="loc_cloud_ShareBasedPaymentArrangementTrancheSixMember_bd414e42-9d9f-49d0-822e-a835e212dd6f" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/StockbasedCompensationScheduleofRestrictedStockUnitsActivityDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#StockbasedCompensationScheduleofRestrictedStockUnitsActivityDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/StockbasedCompensationScheduleofRestrictedStockUnitsActivityDetails" xlink:type="extended" id="i3c45093cd9154bf18f6f74a81a83646c_StockbasedCompensationScheduleofRestrictedStockUnitsActivityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_97b007e1-af1a-4b23-b426-2f4a43a00e29" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_b97dcc5a-7d92-46c0-a562-9bb97bf1682b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_97b007e1-af1a-4b23-b426-2f4a43a00e29" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_b97dcc5a-7d92-46c0-a562-9bb97bf1682b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_1fafa7ed-f975-45dd-bcb1-67ed3672cba4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_b97dcc5a-7d92-46c0-a562-9bb97bf1682b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_1fafa7ed-f975-45dd-bcb1-67ed3672cba4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_efd21f21-161b-4612-ab5a-f0d42ec78931" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_b97dcc5a-7d92-46c0-a562-9bb97bf1682b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_efd21f21-161b-4612-ab5a-f0d42ec78931" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_66f71b51-eb83-48f7-a138-babe19cc7236" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_b97dcc5a-7d92-46c0-a562-9bb97bf1682b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_66f71b51-eb83-48f7-a138-babe19cc7236" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_60a41d7b-312f-43c5-b6b8-8de94af6aba8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_b97dcc5a-7d92-46c0-a562-9bb97bf1682b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_60a41d7b-312f-43c5-b6b8-8de94af6aba8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_b7a55eb5-689f-4345-9fad-6f981ba47b06" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndNotYetReleasedNumber_2714df10-29dc-473c-b523-c324d2198cbe" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndNotYetReleasedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_97b007e1-af1a-4b23-b426-2f4a43a00e29" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndNotYetReleasedNumber_2714df10-29dc-473c-b523-c324d2198cbe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber_96464e90-84a4-48ed-b589-4b0735e5e066" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_97b007e1-af1a-4b23-b426-2f4a43a00e29" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber_96464e90-84a4-48ed-b589-4b0735e5e066" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_b80e31d0-fa46-42ff-8b78-2bef4651dfe3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_97b007e1-af1a-4b23-b426-2f4a43a00e29" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_b80e31d0-fa46-42ff-8b78-2bef4651dfe3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_9c9842d6-e441-4c4f-9a3b-2b4658ae097c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_b80e31d0-fa46-42ff-8b78-2bef4651dfe3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_9c9842d6-e441-4c4f-9a3b-2b4658ae097c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_4d2c71c2-5477-461f-8f3a-76797fe3c9c9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_b80e31d0-fa46-42ff-8b78-2bef4651dfe3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_4d2c71c2-5477-461f-8f3a-76797fe3c9c9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_2ce8b44c-3637-4d71-926f-c3e1d0f02eb3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_b80e31d0-fa46-42ff-8b78-2bef4651dfe3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_2ce8b44c-3637-4d71-926f-c3e1d0f02eb3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_c88e9b10-9875-4f45-8808-7dbad3523606" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_b80e31d0-fa46-42ff-8b78-2bef4651dfe3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_c88e9b10-9875-4f45-8808-7dbad3523606" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_9d62a850-c50b-48e9-9a37-3a3aebaf92de" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndNotYetRealizedWeightedAverageGrantDateFairValue_c8837d08-0e47-4c2f-9084-99255f840adc" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndNotYetRealizedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_97b007e1-af1a-4b23-b426-2f4a43a00e29" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndNotYetRealizedWeightedAverageGrantDateFairValue_c8837d08-0e47-4c2f-9084-99255f840adc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageGrantDateFairValue_17857dab-87f5-4b72-9379-1cc2d5164ede" xlink:href="cloud-20220331.xsd#cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_97b007e1-af1a-4b23-b426-2f4a43a00e29" xlink:to="loc_cloud_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageGrantDateFairValue_17857dab-87f5-4b72-9379-1cc2d5164ede" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c7b99837-1757-42b2-b88a-7b8e761d1df0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_97b007e1-af1a-4b23-b426-2f4a43a00e29" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c7b99837-1757-42b2-b88a-7b8e761d1df0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_7ba43012-c2e4-40e2-b15b-92a755b1d16b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_c7b99837-1757-42b2-b88a-7b8e761d1df0" xlink:to="loc_us-gaap_AwardTypeAxis_7ba43012-c2e4-40e2-b15b-92a755b1d16b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7ba43012-c2e4-40e2-b15b-92a755b1d16b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_7ba43012-c2e4-40e2-b15b-92a755b1d16b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7ba43012-c2e4-40e2-b15b-92a755b1d16b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9158a57a-54ff-440f-9130-489e49d379f6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_7ba43012-c2e4-40e2-b15b-92a755b1d16b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9158a57a-54ff-440f-9130-489e49d379f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_RestrictedStockAndRestrictedStockUnitsMember_8bac41df-6c72-40f2-a7a8-4bf274846165" xlink:href="cloud-20220331.xsd#cloud_RestrictedStockAndRestrictedStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9158a57a-54ff-440f-9130-489e49d379f6" xlink:to="loc_cloud_RestrictedStockAndRestrictedStockUnitsMember_8bac41df-6c72-40f2-a7a8-4bf274846165" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_c8bfb138-dc15-45d7-a60b-f08cf4bb4839" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9158a57a-54ff-440f-9130-489e49d379f6" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_c8bfb138-dc15-45d7-a60b-f08cf4bb4839" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_aef647ac-5f7a-4198-9ccd-742e8496b3e4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9158a57a-54ff-440f-9130-489e49d379f6" xlink:to="loc_us-gaap_RestrictedStockMember_aef647ac-5f7a-4198-9ccd-742e8496b3e4" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/StockbasedCompensationScheduleofFairValueAssumptionsforEmployeeStockPurchasePlanDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#StockbasedCompensationScheduleofFairValueAssumptionsforEmployeeStockPurchasePlanDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/StockbasedCompensationScheduleofFairValueAssumptionsforEmployeeStockPurchasePlanDetails" xlink:type="extended" id="i3acd25ee7ad447b58cce5515bd58f6e9_StockbasedCompensationScheduleofFairValueAssumptionsforEmployeeStockPurchasePlanDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0a42411c-c247-44d3-825a-b88f35557b38" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_9115f05b-8160-4b19-b3b4-a4ef7408ffe3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0a42411c-c247-44d3-825a-b88f35557b38" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_9115f05b-8160-4b19-b3b4-a4ef7408ffe3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_5f03ac5a-6abf-45db-9b16-8a8cca32d259" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0a42411c-c247-44d3-825a-b88f35557b38" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_5f03ac5a-6abf-45db-9b16-8a8cca32d259" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_d4a6655b-ce4d-4a50-ad70-daf1a87a31ee" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0a42411c-c247-44d3-825a-b88f35557b38" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_d4a6655b-ce4d-4a50-ad70-daf1a87a31ee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_e166dcb4-3cd5-4765-bde2-5825786415e7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0a42411c-c247-44d3-825a-b88f35557b38" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_e166dcb4-3cd5-4765-bde2-5825786415e7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_dcaa3135-f489-449f-9130-339765384d26" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0a42411c-c247-44d3-825a-b88f35557b38" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_dcaa3135-f489-449f-9130-339765384d26" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_15e6cf84-ea27-446b-a798-198fb5611341" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_dcaa3135-f489-449f-9130-339765384d26" xlink:to="loc_us-gaap_AwardTypeAxis_15e6cf84-ea27-446b-a798-198fb5611341" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_15e6cf84-ea27-446b-a798-198fb5611341_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_15e6cf84-ea27-446b-a798-198fb5611341" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_15e6cf84-ea27-446b-a798-198fb5611341_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_756499e4-dc87-4a50-838e-80ae0c458554" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_15e6cf84-ea27-446b-a798-198fb5611341" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_756499e4-dc87-4a50-838e-80ae0c458554" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_1e91551a-e2bc-4323-9fa9-58934ecbe2d4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_756499e4-dc87-4a50-838e-80ae0c458554" xlink:to="loc_us-gaap_EmployeeStockMember_1e91551a-e2bc-4323-9fa9-58934ecbe2d4" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/StockbasedCompensationScheduleofStockbasedCompensationExpenseDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#StockbasedCompensationScheduleofStockbasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/StockbasedCompensationScheduleofStockbasedCompensationExpenseDetails" xlink:type="extended" id="idf9298c7e7ab4eceb5abe57847d1c095_StockbasedCompensationScheduleofStockbasedCompensationExpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_73d8ab64-bf9c-4506-aae8-51c120ea1a4b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_a19a1525-77e0-4288-aa4d-4435a4db24c7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_73d8ab64-bf9c-4506-aae8-51c120ea1a4b" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_a19a1525-77e0-4288-aa4d-4435a4db24c7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_e3b91838-0691-46d5-938a-6c3f2dcb2a79" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_73d8ab64-bf9c-4506-aae8-51c120ea1a4b" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_e3b91838-0691-46d5-938a-6c3f2dcb2a79" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_243d8485-ac78-46d2-baa1-d79ab815edd6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_e3b91838-0691-46d5-938a-6c3f2dcb2a79" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_243d8485-ac78-46d2-baa1-d79ab815edd6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_243d8485-ac78-46d2-baa1-d79ab815edd6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_243d8485-ac78-46d2-baa1-d79ab815edd6" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_243d8485-ac78-46d2-baa1-d79ab815edd6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_4b516729-6457-46d7-99c4-9ad1fef83ef0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_243d8485-ac78-46d2-baa1-d79ab815edd6" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_4b516729-6457-46d7-99c4-9ad1fef83ef0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_c3f71d7e-1d71-4ab6-8e7f-36bd2ded52a9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4b516729-6457-46d7-99c4-9ad1fef83ef0" xlink:to="loc_us-gaap_CostOfSalesMember_c3f71d7e-1d71-4ab6-8e7f-36bd2ded52a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpenseMember_1c254ddc-bf42-4b3d-abcf-0cf95137b533" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SellingAndMarketingExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4b516729-6457-46d7-99c4-9ad1fef83ef0" xlink:to="loc_us-gaap_SellingAndMarketingExpenseMember_1c254ddc-bf42-4b3d-abcf-0cf95137b533" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_9eb33176-b32e-49d5-8079-a470d76557f7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4b516729-6457-46d7-99c4-9ad1fef83ef0" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_9eb33176-b32e-49d5-8079-a470d76557f7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_81ea076e-94df-4f10-b94f-fe860c62e146" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4b516729-6457-46d7-99c4-9ad1fef83ef0" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_81ea076e-94df-4f10-b94f-fe860c62e146" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/NetLossperShareAttributabletoCommonStockholdersScheduleofComputationofBasicandDilutedEarningsperShareAttributabletoCommonStockholdersDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#NetLossperShareAttributabletoCommonStockholdersScheduleofComputationofBasicandDilutedEarningsperShareAttributabletoCommonStockholdersDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/NetLossperShareAttributabletoCommonStockholdersScheduleofComputationofBasicandDilutedEarningsperShareAttributabletoCommonStockholdersDetails" xlink:type="extended" id="ic2cb5c713a4c4ece8a7e8546277b405f_NetLossperShareAttributabletoCommonStockholdersScheduleofComputationofBasicandDilutedEarningsperShareAttributabletoCommonStockholdersDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasicLineItems_a7b6b411-263d-46c6-aad6-c8296a1fcb69" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareBasicLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_19b2a95f-a056-479e-a495-62f6bf45b0e4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_a7b6b411-263d-46c6-aad6-c8296a1fcb69" xlink:to="loc_us-gaap_NetIncomeLoss_19b2a95f-a056-479e-a495-62f6bf45b0e4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_4e003a93-610d-430c-8d1e-a03052be25ac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_a7b6b411-263d-46c6-aad6-c8296a1fcb69" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_4e003a93-610d-430c-8d1e-a03052be25ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_79861dfe-0fce-4718-8bfd-19d01557a528" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_a7b6b411-263d-46c6-aad6-c8296a1fcb69" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_79861dfe-0fce-4718-8bfd-19d01557a528" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_f454a1eb-d56e-42b2-ab8d-b294410ab0f9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_a7b6b411-263d-46c6-aad6-c8296a1fcb69" xlink:to="loc_us-gaap_EarningsPerShareBasic_f454a1eb-d56e-42b2-ab8d-b294410ab0f9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_d635ffb3-d1e5-49e5-94d5-032512d660de" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_a7b6b411-263d-46c6-aad6-c8296a1fcb69" xlink:to="loc_us-gaap_EarningsPerShareDiluted_d635ffb3-d1e5-49e5-94d5-032512d660de" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_13ec1df6-735a-4d93-9845-0c2a67f8894e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_a7b6b411-263d-46c6-aad6-c8296a1fcb69" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_13ec1df6-735a-4d93-9845-0c2a67f8894e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_8b323586-5f9c-474b-89f0-081b1371e32e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_13ec1df6-735a-4d93-9845-0c2a67f8894e" xlink:to="loc_us-gaap_StatementClassOfStockAxis_8b323586-5f9c-474b-89f0-081b1371e32e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_8b323586-5f9c-474b-89f0-081b1371e32e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_8b323586-5f9c-474b-89f0-081b1371e32e" xlink:to="loc_us-gaap_ClassOfStockDomain_8b323586-5f9c-474b-89f0-081b1371e32e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_027c7f89-213c-4a16-a3ce-563a01e3ccb9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_8b323586-5f9c-474b-89f0-081b1371e32e" xlink:to="loc_us-gaap_ClassOfStockDomain_027c7f89-213c-4a16-a3ce-563a01e3ccb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_876fe664-ecb3-4dd6-b772-26cedf39f73b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_027c7f89-213c-4a16-a3ce-563a01e3ccb9" xlink:to="loc_us-gaap_CommonClassAMember_876fe664-ecb3-4dd6-b772-26cedf39f73b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_d956ef7b-763e-423c-b6a2-b2c8cf23f2bc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_027c7f89-213c-4a16-a3ce-563a01e3ccb9" xlink:to="loc_us-gaap_CommonClassBMember_d956ef7b-763e-423c-b6a2-b2c8cf23f2bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_a1d1c8d9-a456-41bc-8cb7-733959f3b0e1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_13ec1df6-735a-4d93-9845-0c2a67f8894e" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_a1d1c8d9-a456-41bc-8cb7-733959f3b0e1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_a1d1c8d9-a456-41bc-8cb7-733959f3b0e1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_a1d1c8d9-a456-41bc-8cb7-733959f3b0e1" xlink:to="loc_us-gaap_EquityComponentDomain_a1d1c8d9-a456-41bc-8cb7-733959f3b0e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_798eb1aa-736d-49ad-8133-632ff5c0b7d1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_a1d1c8d9-a456-41bc-8cb7-733959f3b0e1" xlink:to="loc_us-gaap_EquityComponentDomain_798eb1aa-736d-49ad-8133-632ff5c0b7d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_6fa17366-3718-4f8d-ad5c-4e5206728c91" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_798eb1aa-736d-49ad-8133-632ff5c0b7d1" xlink:to="loc_us-gaap_CommonStockMember_6fa17366-3718-4f8d-ad5c-4e5206728c91" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/NetLossperShareAttributabletoCommonStockholdersScheduleofPotentialSharesofCommonStockExcludedfromComputationofBasicandDilutedNetLossperShareAttributabletoCommonStockholdersDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#NetLossperShareAttributabletoCommonStockholdersScheduleofPotentialSharesofCommonStockExcludedfromComputationofBasicandDilutedNetLossperShareAttributabletoCommonStockholdersDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/NetLossperShareAttributabletoCommonStockholdersScheduleofPotentialSharesofCommonStockExcludedfromComputationofBasicandDilutedNetLossperShareAttributabletoCommonStockholdersDetails" xlink:type="extended" id="i1944c6f385a04c2caf99935a8479f989_NetLossperShareAttributabletoCommonStockholdersScheduleofPotentialSharesofCommonStockExcludedfromComputationofBasicandDilutedNetLossperShareAttributabletoCommonStockholdersDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_37b31e20-9839-4431-90ac-f7fb7e93080d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_226bf0dd-3e59-4fb1-af1d-b6a03178c65f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_37b31e20-9839-4431-90ac-f7fb7e93080d" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_226bf0dd-3e59-4fb1-af1d-b6a03178c65f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_dca7cfd6-6d2b-40f9-b54d-29845f658d4e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_37b31e20-9839-4431-90ac-f7fb7e93080d" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_dca7cfd6-6d2b-40f9-b54d-29845f658d4e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_097783c5-3916-498d-80c4-e16789f6933a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_dca7cfd6-6d2b-40f9-b54d-29845f658d4e" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_097783c5-3916-498d-80c4-e16789f6933a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_097783c5-3916-498d-80c4-e16789f6933a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_097783c5-3916-498d-80c4-e16789f6933a" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_097783c5-3916-498d-80c4-e16789f6933a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_9ef6ab6d-6cf3-411a-8ad3-ff4b2fd214a3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_097783c5-3916-498d-80c4-e16789f6933a" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_9ef6ab6d-6cf3-411a-8ad3-ff4b2fd214a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2025Member_4df89295-5605-4c49-b9fd-95b9ae0f2729" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_9ef6ab6d-6cf3-411a-8ad3-ff4b2fd214a3" xlink:to="loc_cloud_SeniorConvertibleNotesDue2025Member_4df89295-5605-4c49-b9fd-95b9ae0f2729" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_SeniorConvertibleNotesDue2026Member_a2e4ae03-8d83-4c0a-9eda-ee9cd5562460" xlink:href="cloud-20220331.xsd#cloud_SeniorConvertibleNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_9ef6ab6d-6cf3-411a-8ad3-ff4b2fd214a3" xlink:to="loc_cloud_SeniorConvertibleNotesDue2026Member_a2e4ae03-8d83-4c0a-9eda-ee9cd5562460" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ShareBasedPaymentArrangementSharesSubjectToRepurchaseMember_aee50ea2-0368-484f-b083-36522afd7f9e" xlink:href="cloud-20220331.xsd#cloud_ShareBasedPaymentArrangementSharesSubjectToRepurchaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_9ef6ab6d-6cf3-411a-8ad3-ff4b2fd214a3" xlink:to="loc_cloud_ShareBasedPaymentArrangementSharesSubjectToRepurchaseMember_aee50ea2-0368-484f-b083-36522afd7f9e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_7c95bbe7-fe89-46a2-a7fc-ca344635600d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_9ef6ab6d-6cf3-411a-8ad3-ff4b2fd214a3" xlink:to="loc_us-gaap_EmployeeStockOptionMember_7c95bbe7-fe89-46a2-a7fc-ca344635600d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_RestrictedStockAwardAndRestrictedStockUnitRSUsAwardMember_9df9658b-a3c9-47b7-8ab6-d767b3b18710" xlink:href="cloud-20220331.xsd#cloud_RestrictedStockAwardAndRestrictedStockUnitRSUsAwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_9ef6ab6d-6cf3-411a-8ad3-ff4b2fd214a3" xlink:to="loc_cloud_RestrictedStockAwardAndRestrictedStockUnitRSUsAwardMember_9df9658b-a3c9-47b7-8ab6-d767b3b18710" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_1ba43be0-758d-43c7-89d9-8251c0f16fc3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_9ef6ab6d-6cf3-411a-8ad3-ff4b2fd214a3" xlink:to="loc_us-gaap_EmployeeStockMember_1ba43be0-758d-43c7-89d9-8251c0f16fc3" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/BusinessCombinationsNarrativesDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#BusinessCombinationsNarrativesDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/BusinessCombinationsNarrativesDetails" xlink:type="extended" id="i4c1346b90a464f08b61de08e1cb97e3f_BusinessCombinationsNarrativesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_d5cb4b3a-bd9d-448a-ade6-3f605f976a5b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_d5cb4b3a-bd9d-448a-ade6-3f605f976a5b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_786da5f1-4376-4f40-8d13-806ed9e51797" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_786da5f1-4376-4f40-8d13-806ed9e51797" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAcquiredFromAcquisition_3907f3d3-3bc8-4270-a326-033ed775d355" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAcquiredFromAcquisition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_us-gaap_CashAcquiredFromAcquisition_3907f3d3-3bc8-4270-a326-033ed775d355" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_c176d32a-2f69-4a8d-bfd8-6f1b89c0f882" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_c176d32a-2f69-4a8d-bfd8-6f1b89c0f882" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_BusinessCombinationConsiderationPayable_7921f49f-54c5-4c0c-aa98-cfa92e07edc2" xlink:href="cloud-20220331.xsd#cloud_BusinessCombinationConsiderationPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_cloud_BusinessCombinationConsiderationPayable_7921f49f-54c5-4c0c-aa98-cfa92e07edc2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_BusinessCombinationContingentConsiderationLiabilityPeriod_4a3083e5-9727-4ffd-b242-4cdaca149644" xlink:href="cloud-20220331.xsd#cloud_BusinessCombinationContingentConsiderationLiabilityPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_cloud_BusinessCombinationContingentConsiderationLiabilityPeriod_4a3083e5-9727-4ffd-b242-4cdaca149644" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_BusinessCombinationPaymentsToSettleAcquireesEquityRelatedAgreements_30df392a-8c29-42de-b2f4-2f34ee4711ab" xlink:href="cloud-20220331.xsd#cloud_BusinessCombinationPaymentsToSettleAcquireesEquityRelatedAgreements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_cloud_BusinessCombinationPaymentsToSettleAcquireesEquityRelatedAgreements_30df392a-8c29-42de-b2f4-2f34ee4711ab" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_BusinessCombinationCompensationArrangements_aac6c3ba-b311-4705-b66d-3800cd77db9d" xlink:href="cloud-20220331.xsd#cloud_BusinessCombinationCompensationArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_cloud_BusinessCombinationCompensationArrangements_aac6c3ba-b311-4705-b66d-3800cd77db9d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense_9d3b0acf-00c7-49bb-bbb6-739c50e93efb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense_9d3b0acf-00c7-49bb-bbb6-739c50e93efb" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability_f8b64679-693f-4609-ad0a-50eab3803b2c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability_f8b64679-693f-4609-ad0a-50eab3803b2c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_DeferredCompensationArrangementWeightedAverageRemainingRecognitionPeriod_3b9e9411-b2e1-4bd2-ab83-cbe785bc7540" xlink:href="cloud-20220331.xsd#cloud_DeferredCompensationArrangementWeightedAverageRemainingRecognitionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_cloud_DeferredCompensationArrangementWeightedAverageRemainingRecognitionPeriod_3b9e9411-b2e1-4bd2-ab83-cbe785bc7540" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_428a8211-1a09-4b86-8ed7-b545bf475583" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_428a8211-1a09-4b86-8ed7-b545bf475583" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_ffafad56-605d-493b-8a0c-e32bf4b663e5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_ffafad56-605d-493b-8a0c-e32bf4b663e5" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfNotesPayable_ee819d99-5945-43f8-932b-91b054c9e060" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RepaymentsOfNotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_us-gaap_RepaymentsOfNotesPayable_ee819d99-5945-43f8-932b-91b054c9e060" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_a1e1e04e-f255-4cd8-8d3c-a5f1c94c825d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GoodwillPurchaseAccountingAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_a1e1e04e-f255-4cd8-8d3c-a5f1c94c825d" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5a50a476-d795-42ad-82d7-fdb65f659453" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_7aadb503-d873-4718-a0bc-559eb59d0ac1" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5a50a476-d795-42ad-82d7-fdb65f659453" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_74032c48-0a36-4f8c-8fb9-529fe607791f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5a50a476-d795-42ad-82d7-fdb65f659453" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_74032c48-0a36-4f8c-8fb9-529fe607791f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_74032c48-0a36-4f8c-8fb9-529fe607791f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_74032c48-0a36-4f8c-8fb9-529fe607791f" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_74032c48-0a36-4f8c-8fb9-529fe607791f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8ee5fa64-061f-4c6e-8653-6feabff00009" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_74032c48-0a36-4f8c-8fb9-529fe607791f" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8ee5fa64-061f-4c6e-8653-6feabff00009" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_VectrixIncMember_5b455f5d-8f85-4719-ab20-1df6ba07654e" xlink:href="cloud-20220331.xsd#cloud_VectrixIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8ee5fa64-061f-4c6e-8653-6feabff00009" xlink:to="loc_cloud_VectrixIncMember_5b455f5d-8f85-4719-ab20-1df6ba07654e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ZarazMember_754545a6-ee32-4919-be22-1e3d5e8a27fc" xlink:href="cloud-20220331.xsd#cloud_ZarazMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8ee5fa64-061f-4c6e-8653-6feabff00009" xlink:to="loc_cloud_ZarazMember_754545a6-ee32-4919-be22-1e3d5e8a27fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_S2SystemsCorporationMember_3e83cd91-7b5f-47a3-8726-f5716ef9b8d2" xlink:href="cloud-20220331.xsd#cloud_S2SystemsCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8ee5fa64-061f-4c6e-8653-6feabff00009" xlink:to="loc_cloud_S2SystemsCorporationMember_3e83cd91-7b5f-47a3-8726-f5716ef9b8d2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_1263f984-ad8f-4ca0-b56d-4701138c2341" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5a50a476-d795-42ad-82d7-fdb65f659453" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_1263f984-ad8f-4ca0-b56d-4701138c2341" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1263f984-ad8f-4ca0-b56d-4701138c2341_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_1263f984-ad8f-4ca0-b56d-4701138c2341" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1263f984-ad8f-4ca0-b56d-4701138c2341_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ffb2557f-5f57-4e84-98b2-3bec0ceb35fe" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_1263f984-ad8f-4ca0-b56d-4701138c2341" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ffb2557f-5f57-4e84-98b2-3bec0ceb35fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_575a9159-282a-4e42-b082-31e6fd424867" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ffb2557f-5f57-4e84-98b2-3bec0ceb35fe" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_575a9159-282a-4e42-b082-31e6fd424867" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/BusinessCombinationsScheduleofAssetsAcquiredandLiabilitiesAssumedDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#BusinessCombinationsScheduleofAssetsAcquiredandLiabilitiesAssumedDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/BusinessCombinationsScheduleofAssetsAcquiredandLiabilitiesAssumedDetails" xlink:type="extended" id="ie48f23f8e6804e26b99a8d9d7ca7935d_BusinessCombinationsScheduleofAssetsAcquiredandLiabilitiesAssumedDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_eedc2369-3205-4e42-ade5-8e819528c06a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_5d65f8c7-8d98-44ee-954c-dd52295d3ce6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_eedc2369-3205-4e42-ade5-8e819528c06a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_5d65f8c7-8d98-44ee-954c-dd52295d3ce6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_9b12c1f1-71a1-4211-a2e8-691becd1381b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_eedc2369-3205-4e42-ade5-8e819528c06a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_9b12c1f1-71a1-4211-a2e8-691becd1381b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_713a6b65-828f-4682-999d-ba63c91efeef" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_eedc2369-3205-4e42-ade5-8e819528c06a" xlink:to="loc_us-gaap_Goodwill_713a6b65-828f-4682-999d-ba63c91efeef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsIncludingGoodwill_542a6197-dc4b-4599-afd2-a7ddbea705d2" xlink:href="cloud-20220331.xsd#cloud_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsIncludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_eedc2369-3205-4e42-ade5-8e819528c06a" xlink:to="loc_cloud_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsIncludingGoodwill_542a6197-dc4b-4599-afd2-a7ddbea705d2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_503e4034-c455-43f9-9c65-711acf0c6512" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_eedc2369-3205-4e42-ade5-8e819528c06a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_503e4034-c455-43f9-9c65-711acf0c6512" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedCompensation_4a8cad80-73f8-4bab-bc4f-8b222c19ab97" xlink:href="cloud-20220331.xsd#cloud_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_eedc2369-3205-4e42-ade5-8e819528c06a" xlink:to="loc_cloud_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedCompensation_4a8cad80-73f8-4bab-bc4f-8b222c19ab97" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_ae5de110-efe0-4f68-ba68-92011f98232a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_eedc2369-3205-4e42-ade5-8e819528c06a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_ae5de110-efe0-4f68-ba68-92011f98232a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_9d543113-2754-4ab5-80a0-3db72681648b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_eedc2369-3205-4e42-ade5-8e819528c06a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_9d543113-2754-4ab5-80a0-3db72681648b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_06c6265c-0936-41a6-920b-26e86cb1e52f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_eedc2369-3205-4e42-ade5-8e819528c06a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_06c6265c-0936-41a6-920b-26e86cb1e52f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_e7bcdf44-e6bd-40e3-98bb-d37cedf63dc1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_eedc2369-3205-4e42-ade5-8e819528c06a" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_e7bcdf44-e6bd-40e3-98bb-d37cedf63dc1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_5d3b6581-29f0-41fc-a274-d0d9e008a984" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_e7bcdf44-e6bd-40e3-98bb-d37cedf63dc1" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_5d3b6581-29f0-41fc-a274-d0d9e008a984" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5d3b6581-29f0-41fc-a274-d0d9e008a984_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5d3b6581-29f0-41fc-a274-d0d9e008a984" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5d3b6581-29f0-41fc-a274-d0d9e008a984_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_13aa819b-b0ea-4932-b4d1-ace509286201" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5d3b6581-29f0-41fc-a274-d0d9e008a984" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_13aa819b-b0ea-4932-b4d1-ace509286201" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_VectrixIncMember_7d67c4cf-7c65-4d60-a7ad-a230c1d73dcb" xlink:href="cloud-20220331.xsd#cloud_VectrixIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_13aa819b-b0ea-4932-b4d1-ace509286201" xlink:to="loc_cloud_VectrixIncMember_7d67c4cf-7c65-4d60-a7ad-a230c1d73dcb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_ZarazMember_c704fce6-5ba5-497c-a878-20d043f1422b" xlink:href="cloud-20220331.xsd#cloud_ZarazMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_13aa819b-b0ea-4932-b4d1-ace509286201" xlink:to="loc_cloud_ZarazMember_c704fce6-5ba5-497c-a878-20d043f1422b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_S2SystemsCorporationMember_415c7d5c-0cbd-464b-930f-3e70f410794d" xlink:href="cloud-20220331.xsd#cloud_S2SystemsCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_13aa819b-b0ea-4932-b4d1-ace509286201" xlink:to="loc_cloud_S2SystemsCorporationMember_415c7d5c-0cbd-464b-930f-3e70f410794d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_f782f9a6-4622-446e-ab15-9c12ae362ea0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_e7bcdf44-e6bd-40e3-98bb-d37cedf63dc1" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_f782f9a6-4622-446e-ab15-9c12ae362ea0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f782f9a6-4622-446e-ab15-9c12ae362ea0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_f782f9a6-4622-446e-ab15-9c12ae362ea0" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f782f9a6-4622-446e-ab15-9c12ae362ea0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_c2258716-82f7-42ae-81eb-eac8a9b5acfd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_f782f9a6-4622-446e-ab15-9c12ae362ea0" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_c2258716-82f7-42ae-81eb-eac8a9b5acfd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_1d26e292-8e9c-4054-820a-7292af7d7601" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_c2258716-82f7-42ae-81eb-eac8a9b5acfd" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_1d26e292-8e9c-4054-820a-7292af7d7601" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/SegmentandGeographicInformationScheduleofPropertyandEquipmentNetbyGeographicAreaDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#SegmentandGeographicInformationScheduleofPropertyandEquipmentNetbyGeographicAreaDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/SegmentandGeographicInformationScheduleofPropertyandEquipmentNetbyGeographicAreaDetails" xlink:type="extended" id="ib07f920d330740baa17e5fd1058c8663_SegmentandGeographicInformationScheduleofPropertyandEquipmentNetbyGeographicAreaDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_3dacd9f1-ef2c-44ce-9060-17e5e171abf3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_9d1a2b76-e9ca-4f8f-a712-5710083e8b19" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3dacd9f1-ef2c-44ce-9060-17e5e171abf3" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_9d1a2b76-e9ca-4f8f-a712-5710083e8b19" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_59b3bfbf-5a9b-40d1-b80d-db27e02f0c37" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3dacd9f1-ef2c-44ce-9060-17e5e171abf3" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_59b3bfbf-5a9b-40d1-b80d-db27e02f0c37" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_ac956c2b-5c23-44b5-95b6-9facaeb3ecc7" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_59b3bfbf-5a9b-40d1-b80d-db27e02f0c37" xlink:to="loc_srt_StatementGeographicalAxis_ac956c2b-5c23-44b5-95b6-9facaeb3ecc7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_ac956c2b-5c23-44b5-95b6-9facaeb3ecc7_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_ac956c2b-5c23-44b5-95b6-9facaeb3ecc7" xlink:to="loc_srt_SegmentGeographicalDomain_ac956c2b-5c23-44b5-95b6-9facaeb3ecc7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_007e919e-cedb-4287-b1ec-2b0d75b680f4" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_ac956c2b-5c23-44b5-95b6-9facaeb3ecc7" xlink:to="loc_srt_SegmentGeographicalDomain_007e919e-cedb-4287-b1ec-2b0d75b680f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_57135c38-bdd7-48f6-b9da-cc445f5dc8f6" xlink:href="https://xbrl.sec.gov/country/2021/country-2021.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_007e919e-cedb-4287-b1ec-2b0d75b680f4" xlink:to="loc_country_US_57135c38-bdd7-48f6-b9da-cc445f5dc8f6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_2def5580-2ae4-46ac-9b11-fd84e2f2f0c3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_007e919e-cedb-4287-b1ec-2b0d75b680f4" xlink:to="loc_us-gaap_NonUsMember_2def5580-2ae4-46ac-9b11-fd84e2f2f0c3" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.cloudflare.com/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="cloud-20220331.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://www.cloudflare.com/role/SubsequentEventsDetails" xlink:type="extended" id="if74e41c876bc4939823ac837050e07e3_SubsequentEventsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_30208357-2a64-47fb-8dca-f1edf3b149ec" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_8ab6ea0e-55ae-433f-8f1a-415be615fc2e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_30208357-2a64-47fb-8dca-f1edf3b149ec" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_8ab6ea0e-55ae-433f-8f1a-415be615fc2e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_BusinessCombinationConsiderationPayableInCommonStockPercentage_b03e21af-c03e-4c13-b25a-d885f98d895c" xlink:href="cloud-20220331.xsd#cloud_BusinessCombinationConsiderationPayableInCommonStockPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_30208357-2a64-47fb-8dca-f1edf3b149ec" xlink:to="loc_cloud_BusinessCombinationConsiderationPayableInCommonStockPercentage_b03e21af-c03e-4c13-b25a-d885f98d895c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_242999f2-4d50-4575-9aa2-5281021d7f8a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_30208357-2a64-47fb-8dca-f1edf3b149ec" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_242999f2-4d50-4575-9aa2-5281021d7f8a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_9d5f7afb-1c0e-40f9-9ad4-103fda7fac56" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_30208357-2a64-47fb-8dca-f1edf3b149ec" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_9d5f7afb-1c0e-40f9-9ad4-103fda7fac56" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_d8561215-1446-497e-8e58-e53931697fae" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_30208357-2a64-47fb-8dca-f1edf3b149ec" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_d8561215-1446-497e-8e58-e53931697fae" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_8936860a-1910-4f7e-b41a-f693eded6fcd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_30208357-2a64-47fb-8dca-f1edf3b149ec" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_8936860a-1910-4f7e-b41a-f693eded6fcd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_4a88c341-ce07-4118-81fc-add11a9da427" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_30208357-2a64-47fb-8dca-f1edf3b149ec" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_4a88c341-ce07-4118-81fc-add11a9da427" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_8c03354b-2a78-48f2-8efc-46a6f57b2ce0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_30208357-2a64-47fb-8dca-f1edf3b149ec" xlink:to="loc_us-gaap_SubsequentEventTable_8c03354b-2a78-48f2-8efc-46a6f57b2ce0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_75bb64c3-1207-4d1f-be07-10fec38a7e31" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_8c03354b-2a78-48f2-8efc-46a6f57b2ce0" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_75bb64c3-1207-4d1f-be07-10fec38a7e31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_75bb64c3-1207-4d1f-be07-10fec38a7e31_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_75bb64c3-1207-4d1f-be07-10fec38a7e31" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_75bb64c3-1207-4d1f-be07-10fec38a7e31_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3c6f518c-c7ad-4c7d-8833-29f49cf63e30" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_75bb64c3-1207-4d1f-be07-10fec38a7e31" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3c6f518c-c7ad-4c7d-8833-29f49cf63e30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_Area1SecurityIncMember_6e826e77-1c52-48e5-88dd-a0cdfcb349d7" xlink:href="cloud-20220331.xsd#cloud_Area1SecurityIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3c6f518c-c7ad-4c7d-8833-29f49cf63e30" xlink:to="loc_cloud_Area1SecurityIncMember_6e826e77-1c52-48e5-88dd-a0cdfcb349d7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_1fcb2aed-8a31-4dd9-b14f-ed683f896c9b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_8c03354b-2a78-48f2-8efc-46a6f57b2ce0" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_1fcb2aed-8a31-4dd9-b14f-ed683f896c9b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_1fcb2aed-8a31-4dd9-b14f-ed683f896c9b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1fcb2aed-8a31-4dd9-b14f-ed683f896c9b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_1fcb2aed-8a31-4dd9-b14f-ed683f896c9b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_3fcf1e5b-1566-46c0-b6fe-4484ca8a02fe" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1fcb2aed-8a31-4dd9-b14f-ed683f896c9b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_3fcf1e5b-1566-46c0-b6fe-4484ca8a02fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_40e3bbe0-b48c-461b-9d85-9c3c54874ad2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_3fcf1e5b-1566-46c0-b6fe-4484ca8a02fe" xlink:to="loc_us-gaap_SubsequentEventMember_40e3bbe0-b48c-461b-9d85-9c3c54874ad2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1b6c3518-dc69-4b1a-b5d3-7a28c5f9bf85" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_8c03354b-2a78-48f2-8efc-46a6f57b2ce0" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1b6c3518-dc69-4b1a-b5d3-7a28c5f9bf85" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_1b6c3518-dc69-4b1a-b5d3-7a28c5f9bf85_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1b6c3518-dc69-4b1a-b5d3-7a28c5f9bf85" xlink:to="loc_us-gaap_ClassOfStockDomain_1b6c3518-dc69-4b1a-b5d3-7a28c5f9bf85_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_de3947ab-f1a9-4cff-9a38-a603e66bbd44" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1b6c3518-dc69-4b1a-b5d3-7a28c5f9bf85" xlink:to="loc_us-gaap_ClassOfStockDomain_de3947ab-f1a9-4cff-9a38-a603e66bbd44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_c41502f4-c68b-41a6-8b02-1a7f459e5fe5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_de3947ab-f1a9-4cff-9a38-a603e66bbd44" xlink:to="loc_us-gaap_CommonClassAMember_c41502f4-c68b-41a6-8b02-1a7f459e5fe5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_cca3d3ba-4595-4363-822f-50e9e997a3ac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_8c03354b-2a78-48f2-8efc-46a6f57b2ce0" xlink:to="loc_us-gaap_AwardTypeAxis_cca3d3ba-4595-4363-822f-50e9e997a3ac" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cca3d3ba-4595-4363-822f-50e9e997a3ac_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_cca3d3ba-4595-4363-822f-50e9e997a3ac" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cca3d3ba-4595-4363-822f-50e9e997a3ac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_57f4cb11-6cee-4718-8d99-0c11a67424d5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_cca3d3ba-4595-4363-822f-50e9e997a3ac" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_57f4cb11-6cee-4718-8d99-0c11a67424d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_895ab744-a1a6-4c12-821f-7824236ace52" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_57f4cb11-6cee-4718-8d99-0c11a67424d5" xlink:to="loc_us-gaap_EmployeeStockOptionMember_895ab744-a1a6-4c12-821f-7824236ace52" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_8bcd9972-d111-45ae-a1b9-411003821785" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_8c03354b-2a78-48f2-8efc-46a6f57b2ce0" xlink:to="loc_us-gaap_PlanNameAxis_8bcd9972-d111-45ae-a1b9-411003821785" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_8bcd9972-d111-45ae-a1b9-411003821785_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_8bcd9972-d111-45ae-a1b9-411003821785" xlink:to="loc_us-gaap_PlanNameDomain_8bcd9972-d111-45ae-a1b9-411003821785_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_39d011f4-cabe-4562-b358-ee9731d4f768" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_8bcd9972-d111-45ae-a1b9-411003821785" xlink:to="loc_us-gaap_PlanNameDomain_39d011f4-cabe-4562-b358-ee9731d4f768" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cloud_TwoThousandAndNineteenEquityIncentivePlanMember_fd58d130-629d-44f0-a397-b1d7bd59faab" xlink:href="cloud-20220331.xsd#cloud_TwoThousandAndNineteenEquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_39d011f4-cabe-4562-b358-ee9731d4f768" xlink:to="loc_cloud_TwoThousandAndNineteenEquityIncentivePlanMember_fd58d130-629d-44f0-a397-b1d7bd59faab" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-roles-2021-01-31.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfAdoptionMember" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TypeOfAdoptionMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountingStandardsUpdate202006Member" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountingStandardsUpdate202006Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember" xlink:to="loc_us-gaap_AccountingStandardsUpdate202006Member" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
