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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2005-01-25</periodOfReport>

    <dateOfOriginalSubmission>2005-02-11</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <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>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</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>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Affiliate of Director</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001318616</rptOwnerCik>
            <rptOwnerName>Epstein David</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>TWO EMBARCADERO</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 2200</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94111</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Affiliate of Director</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001318214</rptOwnerCik>
            <rptOwnerName>Feuille James</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>TWO EMBARCADERO</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 2200</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94111</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</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>0</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>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</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>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-01-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F5"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4135</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F5"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4135</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F5"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-02-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F6"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>154350</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F6"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1733423</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Notes</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-02-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F7"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>700</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F7"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>700</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The reporting persons (the &quot;Reporting Persons&quot;) are Crosslink Capital, Inc. (&quot;Crosslink&quot;), Crossover Fund III Management, L.L.C. (&quot;Crossover III Management&quot;), Crosslink Ventures IV Holdings, L.L.C. (&quot;Ventures IV Holdings&quot;), Crosslink Verwaltungs GmbH (&quot;Verwaltungs&quot;), Michael J. Stark, Seymour F. Kaufman, Jim Feuille, Dave Epstein, 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="F2">Mr. Stark and Mr. Kaufman are control persons of Crosslink. Mr. Stark, Mr. Kaufman, Mr. Bliska, Mr. Dunn, Mr. Feuille and Mr. Epstein are control persons of Crossover III Management. Mr. Stark is a control person 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="F3">Crosslink, Crossover III Management, Ventures IV Holdings, Verwaltungs, Mr. Stark, Mr. Kaufman, Mr. Feuille, Mr. Epstein, Mr. Dunn, Mr. Bliska and Mr. Hromadko are filing this Form 4 jointly and constitute a group, within the meaning of Rule 13d-5(b) under the Securities Exchange Act of 1934, as amended, but disclaim membership in a group, with any other person. These securities are held directly by investment funds to which Crosslink or Crossover III Management is investment adviser (the &quot;Funds&quot;) for the benefit of the investors in the Funds.</footnote>
        <footnote id="F4">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. Feuille, Mr. Epstein, 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, including the Funds, holds more than 10% of the Issuer's outstanding common stock. The amount in Column 5 includes 34,243 shares beneficially owned directly by the Reporting Persons as of February 11, 2005.</footnote>
        <footnote id="F5">These securities were beneficially owned directly by Mr. Kaufman. They were transferred to his ex-wife as part of a comprehensive division of marital assets in connection with their divorce settlement that became effective on January 25, 2005. The zero in Column 4 is a placeholder only that is required by the EDGAR software.</footnote>
        <footnote id="F6">On February 11, 2005, 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 indirectly 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="F7">These securities were received by Mr. Feuille 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.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Thomas Edward Bliska</signatureName>
        <signatureDate>2005-03-02</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Daniel John Dunn</signatureName>
        <signatureDate>2005-03-02</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>David Epstein</signatureName>
        <signatureDate>2005-03-02</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>James Feuille</signatureName>
        <signatureDate>2005-03-02</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Gary Hromadko</signatureName>
        <signatureDate>2005-03-02</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Seymour F. Kaufman</signatureName>
        <signatureDate>2005-03-02</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Michael J. Stark</signatureName>
        <signatureDate>2005-03-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
