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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-09-08</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001062292</issuerCik>
        <issuerName>KNOT INC</issuerName>
        <issuerTradingSymbol>KNOT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001026179</rptOwnerCik>
            <rptOwnerName>Federated Retail Holdings Inc</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>7 WEST SEVENTH STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CINCINNATI</rptOwnerCity>
            <rptOwnerState>OH</rptOwnerState>
            <rptOwnerZipCode>45202</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-09-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>86740</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3662487</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Wholly owned subsidiary</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">As a result of the September 8, 2006 merger of WeddingChannel.com, Inc. and The Knot, Inc., the 9,487,112 shares of WeddingChannel.com owned by Federated Corporate Services, Inc. were converted into the right to receive 86,740 shares of The Knot, Inc. and $4,169,562 in cash.</footnote>
        <footnote id="F2">Prior to the acquisition by Federated Department Stores, Inc. (&quot;Federated&quot;), The May Department Stores Company, a Delaware corporation (&quot;May&quot;) owned 3,575,747 shares of The Knot, Inc. in the name of The May Department Stores Company, a New York corporation (now known as Federated Retail Holdings, Inc. (&quot;FRHI&quot;)).  Following the acquisition of May, Federated transferred ownership of these shares from FRHI to Federated Corporate Services, Inc.</footnote>
        <footnote id="F3">Federated Retail Holdings, Inc. (formerly known as The May Department Stores Company) owns the shares of The Knot, Inc. in the name of its wholly owned subsidiary, Federated Corporate Services, Inc.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/Dennis J. Broderick, President, Federated Retail Holdings, Inc.</signatureName>
        <signatureDate>2007-02-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
