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

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    <periodOfReport>2015-10-01</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001478484</issuerCik>
        <issuerName>zulily, inc.</issuerName>
        <issuerTradingSymbol>ZU</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001191203</rptOwnerCik>
            <rptOwnerName>CARLBORG W ERIC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2480 SAND HILL ROAD, SUITE #101</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MENLO PARK</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94025</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

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            </underlyingSecurity>
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            <securityTitle>
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                <value>Stock Option (Right to Buy)</value>
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                <value></value>
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                    <value>10368</value>
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                <underlyingSecurityShares>
                    <value>10368</value>
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    <footnotes>
        <footnote id="F1">Per the terms of the Agreement and Plan of Reorganization, dated August 16, 2015, by and among the Issuer, Liberty Interactive Corporation, a Delaware corporation, Mocha Merger Sub, Inc., a Delaware corporation, and Ziggy Merger Sub, LLC, a Delaware limited liability company (the &quot;Agreement&quot;), this option was assumed by Liberty Interactive Corporation and became an option to purchase a number of shares of Liberty Interactive Corporation's Series A QVC Group Common Stock equal to (i) the number of shares set forth in Column 5 of Table II multiplied by (ii) the Conversion Ratio (as described below) and rounding the resulting number down to the nearest whole number of shares of Liberty Interactive Corporation's Series A QVC Group Common Stock.  This option's exercise price per share was also adjusted by dividing the exercise price set forth in Column 2 of Table II by the Conversion Ratio, and rounding the resulting exercise price up to the nearest whole cent.</footnote>
        <footnote id="F2">The Conversion Ratio equals (a) 0.3098 plus (b) the quotient of $9.375 divided by the volume weighted average closing sale price of one share of Liberty Interactive Corporation's Series A QVC Group Common Stock as reported over the ten consecutive trading day period ending on and including September 29, 2015.</footnote>
        <footnote id="F3">The vesting schedule of the option remains unchanged.</footnote>
        <footnote id="F4">Each share of Class B Common Stock was convertible at any time at the option of the holder into one share of Class A Common Stock.  In addition, each share of Class B Common Stock would have converted automatically into one share of Class A Common Stock upon any transfer, whether or not for value and whether voluntary or involuntary or by operation of law, except for certain transfers described in the Issuer's Amended and Restated Certificate of Incorporation, including, without limitation, certain transfers for tax and estate planning purposes.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Brian Woodard, Attorney-in-Fact</signatureName>
        <signatureDate>2015-10-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
