<SEC-DOCUMENT>0001562180-21-007081.txt : 20211116
<SEC-HEADER>0001562180-21-007081.hdr.sgml : 20211116
<ACCEPTANCE-DATETIME>20211116165954
ACCESSION NUMBER:		0001562180-21-007081
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20211116
FILED AS OF DATE:		20211116
DATE AS OF CHANGE:		20211116

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Sharan Sharat
		CENTRAL INDEX KEY:			0001841654

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-39965
		FILM NUMBER:		211417027

	MAIL ADDRESS:	
		STREET 1:		3221 LA MESA DRIVE
		CITY:			SAN CARLOS
		STATE:			CA
		ZIP:			94070

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ON24 INC.
		CENTRAL INDEX KEY:			0001110611
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-PREPACKAGED SOFTWARE [7372]
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		50 BEALE STREET, 8TH FLOOR
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94105
		BUSINESS PHONE:		(415) 369-8000

	MAIL ADDRESS:	
		STREET 1:		50 BEALE STREET, 8TH FLOOR
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94105

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ON24 INC
		DATE OF NAME CHANGE:	20000329
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primarydocument.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-11-16</periodOfReport>

    <notSubjectToSection16>false</notSubjectToSection16>

    <issuer>
        <issuerCik>0001110611</issuerCik>
        <issuerName>ON24 INC.</issuerName>
        <issuerTradingSymbol>ONTF</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001841654</rptOwnerCik>
            <rptOwnerName>Sharan Sharat</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ON24, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>50 BEALE STREET, 8TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94015</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>true</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle>President and Chief Executive</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-11-16</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2021-11-16</value>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>14700.00</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>16.9731</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1994747.00</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>92500.00</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Held by daughter</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Shares acquired on the open market.</footnote>
        <footnote id="F2">The price reported in Column 4 is a weighted average price. These shares were acquired in multiple transactions ranging from $16.88 to $17.07, inclusive. The reporting person undertakes to provide to Issuer, any security holder of Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares acquired at each separate price within the ranges set forth in footnote (2) to this Form 4</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Sharat Sharan, William Weesner, Attorney-in-Fact</signatureName>
        <signatureDate>2021-11-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
