<SEC-DOCUMENT>0001595974-17-000067.txt : 20171103
<SEC-HEADER>0001595974-17-000067.hdr.sgml : 20171103
<ACCEPTANCE-DATETIME>20171103173722
ACCESSION NUMBER:		0001595974-17-000067
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		2
CONFORMED PERIOD OF REPORT:	20171026
FILED AS OF DATE:		20171103
DATE AS OF CHANGE:		20171103

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Prusz Joseph R
		CENTRAL INDEX KEY:			0001721039

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36384
		FILM NUMBER:		171177671

	MAIL ADDRESS:	
		STREET 1:		C/O THE RUBICON PROJECT, INC.
		STREET 2:		12181 BLUFF CREEK DRIVE, 4TH FLOOR
		CITY:			PLAYA VISTA
		STATE:			CA
		ZIP:			90094

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			RUBICON PROJECT, INC.
		CENTRAL INDEX KEY:			0001595974
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMPUTER PROGRAMMING, DATA PROCESSING, ETC. [7370]
		IRS NUMBER:				208881738
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		12181 BLUFF CREEK DRIVE, 4TH FLOOR
		CITY:			LOS ANGELES
		STATE:			CA
		ZIP:			90094
		BUSINESS PHONE:		310-207-0272

	MAIL ADDRESS:	
		STREET 1:		12181 BLUFF CREEK DRIVE, 4TH FLOOR
		CITY:			LOS ANGELES
		STATE:			CA
		ZIP:			90094
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>wf-form3_150974502830435.xml
<DESCRIPTION>FORM 3
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2017-10-26</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001595974</issuerCik>
        <issuerName>RUBICON PROJECT, INC.</issuerName>
        <issuerTradingSymbol>RUBI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001721039</rptOwnerCik>
            <rptOwnerName>Prusz Joseph R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O THE RUBICON PROJECT, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>12181 BLUFF CREEK DRIVE, 4TH FL</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90094</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Global Chief Revenue Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>91761</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.7</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2022-12-13</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>16.75</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2025-05-19</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6500.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.06</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2027-03-15</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>18000.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents 15,208 shares of common stock and 76,553 restricted stock units.  The restricted stock units vest as follows: 8,751 on November 15, 2017; 30,311 on May 15, 2018; 11,376 on November 15, 2018; 10,331 on May 15, 2019; 7,346 on November 15, 2019; 4,500 on May 15, 2020; 2,625 on November 15, 2020; and 1,313 on May 15, 2021.</footnote>
        <footnote id="F2">Fully vested.</footnote>
        <footnote id="F3">25% of the stock options vested on February 1, 2016 and the remaining option shares become exercisable in 36 equal installments each calendar month thereafter.</footnote>
        <footnote id="F4">25% of the stock options will vest on February 1, 2018 and the remaining option shares will become exercisable in 36 equal installments each calendar month thereafter.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Jonathan Feldman, attorney-in-fact</signatureName>
        <signatureDate>2017-11-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-24
<SEQUENCE>2
<FILENAME>poa.htm
<DESCRIPTION>POWER OF ATTORNEY
<TEXT>
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<pre>
EXHIBIT 24
POWER OF ATTORNEY
FOR SEC FILINGS ON FORMS ID, 3, 4, 5 AND 144
IN RESPECT OF SECURITIES OF
THE RUBICON PROJECT, INC.
             The undersigned hereby constitutes and appoints Brian Copple, David Day and Jonathan Feldman, and each of them, as his true and lawful attorney-in-fact and agent, with full power of substitution and resubstitution for his in his name and stead in any and all capacities, to sign and file for and on his behalf, in respect of any acquisition, disposition or other change in ownership of any Common Stock of The Rubicon Project, Inc. (the Company), the following:
(i)     any Form ID to be filed with the Securities and Exchange Commission (the SEC);
(ii)    any Initial Statement of Beneficial Ownership of Securities on Form 3 to be filed with the SEC;
(iii)    any Statement of Changes of Beneficial Ownership of Securities on Form 4 to be filed with the SEC;
(iv)    any Annual Statement of Beneficial Ownership of Securities on Form 5 to be filed with the SEC;
(v)    any Notice of Proposed Sale of Securities on Form 144 to be filed with the SEC; and
(vi)    any and all agreements, certificates, receipts, or other documents in connection therewith.
             The undersigned hereby gives full power and authority to the attorney-in-fact to seek and obtain as the undersigneds representative and on the undersigneds behalf, information on transactions in the Companys securities from any third party, including brokers, employee benefit plan administrators and trustees, and the undersigned hereby authorizes any such person to release such information to the undersigned and approves and ratifies any such release of information.
             The undersigned hereby grants unto such attorney-in-fact and agent full power and authority to do and perform each and every act and thing requisite and necessary in connection with such matters and hereby ratifies and confirms all that any such attorney-in-fact and agent or substitute may do or cause to be done by virtue hereof.
             The undersigned acknowledges that:
(i)    neither the Company nor such attorney-in-fact assumes (i) any liability for the undersigneds responsibility to comply with the requirement of the Securities Exchange Act of 1934, as amended (the Exchange Act), (ii) any liability of the undersigned for any failure to comply with such requirements or (iii) any obligation or liability of the undersigned for profit disgorgement under Section 16(b) of the Exchange Act; and
(ii)    this Power of Attorney does not relieve the undersigned from responsibility for compliance with the undersigneds obligations under the Exchange Act, including without limitation the reporting requirements under Section 16 of the Exchange Act.

             This Power of Attorney shall remain in full force and effect until revoked by the undersigned in a signed writing delivered to such attorney-in-fact.
             IN WITNESS WHEREOF, the undersigned has executed this Power of Attorney.

Date:  October 26, 2017    /s/ Joseph R. Prusz






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