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

    <schemaVersion>X0609</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-03-31</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001819989</issuerCik>
        <issuerName>Cipher Digital Inc.</issuerName>
        <issuerTradingSymbol>CIFR</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001887627</rptOwnerCik>
            <rptOwnerName>Iwaschuk William</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>C/O CIPHER DIGITAL INC.</rptOwnerStreet1>
            <rptOwnerStreet2>1 VANDERBILT AVENUE, FLOOR 54</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10017</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Co-President and CLO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

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                <transactionPricePerShare>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>33968</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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        <derivativeTransaction>
            <securityTitle>
                <value>Performance Stock Units</value>
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    <footnotes>
        <footnote id="F1">Each restricted stock unit (&quot;RSU&quot;) represents a contingent right to receive one share of the Issuer's Common Stock.</footnote>
        <footnote id="F2">Each performance stock unit (&quot;PSU&quot;) represents a contingent right to receive one share of Issuer's Common Stock.</footnote>
        <footnote id="F3">The RSUs vest in equal quarterly installments over a three-year period, on March 31, June 30, September 30 and December 15 of each year, subject to the Reporting Person's continuous service on the applicable vesting date. The first vesting date occurred on March 31, 2025.</footnote>
        <footnote id="F4">The RSUs vest in equal quarterly installments over a three-year period, on March 31, June 30, September 30 and December 15 of each year, subject to the Reporting Person's continuous service on the applicable vesting date. The first vesting date occurred on March 31, 2026.</footnote>
        <footnote id="F5">305,707 earned PSUs vested on December 19, 2025, and the remaining earned PSUs vest in substantially equal quarterly installments, subject to the Reporting Person's continuous service on each vesting date. The first such vesting date occurred on March 31, 2026. These earned PSUs have no expiration date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ William Iwaschuk</signatureName>
        <signatureDate>2026-04-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
