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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2012-06-29</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001077866</issuerCik>
        <issuerName>LOOKSMART LTD</issuerName>
        <issuerTradingSymbol>LOOK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001299265</rptOwnerCik>
            <rptOwnerName>Platinum Partners Value Arbitrage Fund, LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O WALKERS CORPORATE SERVICES LIMITED</rptOwnerStreet1>
            <rptOwnerStreet2>WALKER HOUSE, 87 MARY STREET</rptOwnerStreet2>
            <rptOwnerCity>GEORGETOWN, GRAND CAYMAN</rptOwnerCity>
            <rptOwnerState>E9</rptOwnerState>
            <rptOwnerZipCode>KY1-9002</rptOwnerZipCode>
            <rptOwnerStateDescription>CAYMAN ISLANDS</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001368616</rptOwnerCik>
            <rptOwnerName>Platinum Management (NY) LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>152 WEST 57TH STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001339643</rptOwnerCik>
            <rptOwnerName>Nordlicht Mark</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>152 WEAT 57TH STREET</rptOwnerStreet1>
            <rptOwnerStreet2>4TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1728000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Reflects the securities of the issuer owned directly by Platinum Partners Value Arbitrage Fund L.P. (the &quot;Master Fund&quot;).</footnote>
        <footnote id="F2">Platinum Management (NY) LLC (&quot;Platinum Management&quot;) is the investment manager and general partner of the Master Fund.  Mark Nordlicht and Uri Landesman are the controlling persons of Platinum Management.  Platinum Management, Mr. Nordlicht and Uri Landesman may each be deemed to indirectly beneficially own the shares of common stock held by the Master Fund.  For purposes of this Form 3, the Investment Manager and Messrs. Nordlicht and Landesman each disclaims beneficial ownership of the shares of common stock beneficially owned by the Master Fund, except to the extent of its or his pecuniary interest therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Uri Landesman, President of Platinum Management (NY) LLC, as general partner of Platinum Partners Value Arbitrage Fund L.P.</signatureName>
        <signatureDate>2012-07-09</signatureDate>
    </ownerSignature>
</ownershipDocument>
