<SEC-DOCUMENT>0001517413-20-000110.txt : 20200526
<SEC-HEADER>0001517413-20-000110.hdr.sgml : 20200526
<ACCEPTANCE-DATETIME>20200526172506
ACCESSION NUMBER:		0001517413-20-000110
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20200521
FILED AS OF DATE:		20200526
DATE AS OF CHANGE:		20200526

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Maasberg Wolfgang
		CENTRAL INDEX KEY:			0001499654

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-38897
		FILM NUMBER:		20911870

	MAIL ADDRESS:	
		STREET 1:		6401 HOLLIS ST.
		STREET 2:		SUITE 125
		CITY:			EMERYVILLE
		STATE:			CA
		ZIP:			94608

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Fastly, Inc.
		CENTRAL INDEX KEY:			0001517413
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-PREPACKAGED SOFTWARE [7372]
		IRS NUMBER:				275411834
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		475 BRANNAN
		STREET 2:		SUITE 300
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94107
		BUSINESS PHONE:		415-525-3481

	MAIL ADDRESS:	
		STREET 1:		475 BRANNAN
		STREET 2:		SUITE 300
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94107

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Skycache, Inc.(DE)
		DATE OF NAME CHANGE:	20110405
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_159052828957883.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-05-21</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001517413</issuerCik>
        <issuerName>Fastly, Inc.</issuerName>
        <issuerTradingSymbol>FSLY</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001499654</rptOwnerCik>
            <rptOwnerName>Maasberg Wolfgang</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O FASTLY, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>475 BRANNAN STREET, SUITE 300</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94107</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP of Sales</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2020-05-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1204</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>41.43</value>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>210040</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person.</footnote>
        <footnote id="F2">Includes 1,204 shares acquired under the Fastly, Inc. 2019 Employee Stock Purchase Plan on May 20, 2020.</footnote>
        <footnote id="F3">The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $41.30 to $41.54, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Seth Gottlieb, Attorney-in-Fact</signatureName>
        <signatureDate>2020-05-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
