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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-03-09</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000808461</issuerCik>
        <issuerName>GCI LIBERTY, INC.</issuerName>
        <issuerTradingSymbol>GLIBA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001355096</rptOwnerCik>
            <rptOwnerName>Liberty Interactive Corp</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>12300 LIBERTY BOULEVARD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ENGLEWOOD</rptOwnerCity>
            <rptOwnerState>CO</rptOwnerState>
            <rptOwnerZipCode>80112</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2018-03-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>81706919</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class B Common Stock</value>
                <footnoteId id="F3"/>
            </securityTitle>
            <transactionDate>
                <value>2018-03-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4455308</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The transactions reported on this Form relate to the split-off of the Issuer from the Reporting Person effective March 9, 2018. The Reporting Person acquired the shares of the Issuer's Class A common stock, no par value (&quot;GLIBA&quot;), and Class B common stock, no par value (&quot;GLIBB&quot;), on March 9, 2018, pursuant to the terms of an Agreement and Plan of Reorganization, dated as of April 4, 2017, by and among the Reporting Person, Liberty Interactive, LLC, a wholly-owned subsidiary of the Reporting Person (&quot;LI LLC&quot;) and the Issuer, as amended.  In the split-off, the Reporting Person redeemed (i) each outstanding share of its Series A Liberty Ventures common stock for one share of GLIBA and (ii) each outstanding share of its Series B Liberty Ventures common stock for one share of GLIBB. The Reporting Person did not retain any shares of GLIBA or GLIBB following the split-off.</footnote>
        <footnote id="F2">Prior to the split-off, LI LLC distributed the shares of GLIBA and GLIBB to the Reporting Person.</footnote>
        <footnote id="F3">Each share of Class B common stock is convertible, at the holder's election, into one share of Class A common stock, at any time for no consideration other than the surrender of the share of Class B common stock for each share of Class A common stock.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Liberty Interactive Corporation By: /s/ Craig Troyer Title: Senior Vice President, Deputy General Counsel and Assistant Secretary</signatureName>
        <signatureDate>2018-03-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
