<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-10-28</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001101239</issuerCik>
        <issuerName>EQUINIX INC</issuerName>
        <issuerTradingSymbol>EQIX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001104329</rptOwnerCik>
            <rptOwnerName>CROSSLINK CAPITAL INC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>TWO EMBARCADERO CENTER</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 2200</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94111</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Affiliate of Director</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001242229</rptOwnerCik>
            <rptOwnerName>CROSSOVER FUND III MANAGMENT LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1></rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity></rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Affiliate of Director</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001242237</rptOwnerCik>
            <rptOwnerName>CROSSLINK VENTURES IV HOLDINGS LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1></rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity></rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Affiliate of Director</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001242264</rptOwnerCik>
            <rptOwnerName>CROSSLINK VERWALTUNGS GMBH</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1></rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity></rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Affiliate of Director</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001242239</rptOwnerCik>
            <rptOwnerName>STARK MICHAEL J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1></rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity></rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Affiliate of Director</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001242240</rptOwnerCik>
            <rptOwnerName>KAUFMAN SEYMOUR F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1></rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity></rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Affiliate of Director</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001242242</rptOwnerCik>
            <rptOwnerName>BLISKA THOMAS EDWARD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1></rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity></rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Affiliate of Director</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001242244</rptOwnerCik>
            <rptOwnerName>DUNN DANIEL JOHN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1></rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity></rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Affiliate of Director</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001242241</rptOwnerCik>
            <rptOwnerName>JACIMOVIC VLADIMIR S</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1></rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity></rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Affiliate of Director</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001240055</rptOwnerCik>
            <rptOwnerName>HROMADKO GARY</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>301 VELOCITY WAY 5TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>FOSTER CITY</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94404</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-10-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>154350</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2013904</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Notes</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-11-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F6"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>8340</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F6"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2012688</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Notes</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-11-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F7"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>7124</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F7"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2012688</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-11-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>110000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>36.179</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1902688</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Notes</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">On October 28, 2004, investment funds for which Crosslink serves as investment adviser or manager, including funds for which Ventures IV Holdings and Verwaltungs serve as general partner, manager or Class B unitholder, distributed these securities pro rata to the investors in those funds, which securities previously were reported as beneficially owned by the Reporting Persons.  The zero in Column 4 is a placeholder only that is required by the EDGAR software.</footnote>
        <footnote id="F2">The reporting persons (the Reporting Persons) are Crosslink Capital, Inc. (Crosslink), Crossover Fund III Management, L.L.C. (Crossover III Management), Crosslink Ventures IV Holdings, L.L.C. (Ventures IV Holdings), Crosslink Verwaltungs GmbH (Verwaltungs), Michael J. Stark, Seymour F. Kaufman, Vladimir S. Jacimovic, Daniel John Dunn, Thomas Edward Bliska and Gary Hromadko.  Crosslink is an investment adviser to investment funds of which Crossover III Management, Ventures IV Holdings or Verwaltungs is the general partner, manager or the holder of Class B Units, and other investment funds.  Crossover III Management is also the investment adviser to investment funds.</footnote>
        <footnote id="F3">Mr. Stark and Mr. Kaufman are control persons of Crosslink.  Mr. Stark, Mr. Kaufman, Mr. Bliska, Mr. Dunn and Mr. Jacimovic are control persons of Crossover III Management.  Mr. Stark and Mr. Jacimovic are control persons of Ventures IV Holdings and Verwaltungs.  Mr. Hromadko is a member of the Issuer's board of directors and serves as the representative of the Reporting Persons.</footnote>
        <footnote id="F4">Crosslink, Crossover III Management, Ventures IV Holdings, Verwaltungs, Mr. Stark, Mr. Kaufman, Mr. Jacimovic, Mr. Dunn, Mr. Bliska and Mr. Hromadko are filing this Form 4 jointly and constitute a group, but disclaim membership in a group, within the meaning of Rule 13d-5(b) under the Securities Exchange Act of 1934, as amended, with any other person.  These securities are held directly by investment funds to which Crosslink or Crossover III Management is investment adviser (the Funds) for the benefit of the investors in the Funds.</footnote>
        <footnote id="F5">These securities are indirectly beneficially owned by Crosslink or Crossover III Management as the investment adviser to the Funds, by Crossover III Management, Ventures IV Holdings and Verwaltungs as the general partner, manager or holder of Class B Units of the Funds, and by Mr. Stark, Mr. Kaufman, Mr. Jacimovic, Mr. Bliska and Mr. Dunn as the various control persons of those entities.  The Reporting Persons disclaim beneficial ownership of such securities except to the extent of their pecuniary interest therein.  No client of Crosslink or Crossover III Management holds more than 10% of the Issuer's outstanding common stock.  The amount in Column 5 includes 24,941 shares beneficially owned directly by the Reporting Persons as of October 28, 2004, and 17,817 shares beneficially owned directly by them as of November 4 and 5, 2004.</footnote>
        <footnote id="F6">On November 4, 2004, investment funds for which Crosslink serves as investment adviser or manager, including funds for which Ventures IV Holdings serves as manager, distributed these securities pro rata to the investors in those funds, which securities previously were reported as beneficially owned by the Reporting Persons.  Some of those securities were distributed to Reporting Persons as described in Note 7.  The zero in Column 4 is a placeholder only that is required by the EDGAR software.</footnote>
        <footnote id="F7">These securities were received by Reporting Persons for no consideration in the pro rata distribution described in Note 6.  The zero in Column 4 is a placeholder only that is required by the EDGAR software.  The shares reported in Column 5 include 1,982,869 shares beneficially owned indirectly by such Reporting Persons as described in Note 5.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>CrossLink Capital, Inc. by Michael J. Stark, President</signatureName>
        <signatureDate>2004-11-08</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Crossover Fund III Management, LLC by Michael J. Stark, Senior Fund Mgr</signatureName>
        <signatureDate>2004-11-08</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Crosslink Ventures IV Holdings, LLC by Michael J. Stark, Sr. Fund Mgr.</signatureName>
        <signatureDate>2004-11-08</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Crosslink Verwaltungs GmbH by Michael J. Stark, Managing Dir.</signatureName>
        <signatureDate>2004-11-08</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Michael J. Stark</signatureName>
        <signatureDate>2004-11-08</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Seymour F. Kaufman</signatureName>
        <signatureDate>2004-11-08</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Thomas Edward Bliska</signatureName>
        <signatureDate>2004-11-08</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Daniel John Dunn</signatureName>
        <signatureDate>2004-11-08</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Vladimir S. Jacimovic</signatureName>
        <signatureDate>2004-11-08</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Gary Hromadko</signatureName>
        <signatureDate>2004-11-08</signatureDate>
    </ownerSignature>
</ownershipDocument>

