<?xml version="1.0"?><?xml-stylesheet type="text/xsl" href="/Pages/Form4.xsl"?>
<ownershipDocument>

    <schemaVersion>X0305</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2012-06-01</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001395018</rptOwnerCik>
            <rptOwnerName>Smith Stephen M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE LAGOON DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>REDWOOD CITY</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94065</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO &amp; President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2012-06-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>6000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>156.0463</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>39966</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Shares were sold pursuant to a 10b5-1 Trading Plan.</footnote>
        <footnote id="F2">The average price of $156.0463 consists of the following blocks of shares:  100 shares sold at $154.33, 100 at $154.65, 100 at $154.83, 100 at $154.96, 200 at $154.98, 100 at $155.00, 100 at $155.02, 100 at $155.04, 100 at $155.05, 100 at $155.10, 100 at $155.13, 100 at $155.16, 100 at $155.175, 100 at $155.19, 100 at $155.22, 100 at $155.23, 100 at $155.26, 100 at $155.31, 200 at $155.37, 100 at $155.39, 100 at $155.40, 100 at $155.47, 100 at $155.49, 200 at $155.52, 300 at $155.53, 100 at $155.56, 100 at $155.57, 100 at $155.63, 100 at $155.672, 200 at $155.69, 200 at $155.72, 200 at $155.75, 100 at $155.76, 100 at $155.77, 100 at $155.81, 100 at $155.87, 100 at $155.88, 100 at $155.91, 200 at $156.72, 100 at $157.12, 100 at $157.345, 200 at $158.38, 100 at $158.47, 100 at $158.48, 100 at $158.89, 96 at $158.90, 100 at $158.92, 100 at $158.93, 200 at $159.015 and 4 at $159.05.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Darrin B. Short, Attorney-in-Fact</signatureName>
        <signatureDate>2012-06-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
