<SEC-DOCUMENT>0001209191-21-011329.txt : 20210217
<SEC-HEADER>0001209191-21-011329.hdr.sgml : 20210217
<ACCEPTANCE-DATETIME>20210217165753
ACCESSION NUMBER:		0001209191-21-011329
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20210214
FILED AS OF DATE:		20210217
DATE AS OF CHANGE:		20210217

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Bergman Artur
		CENTRAL INDEX KEY:			0001769490

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-38897
		FILM NUMBER:		21645757

	MAIL ADDRESS:	
		STREET 1:		C/O FASTLY, INC.
		STREET 2:		475 BRANNAN STREET, SUITE 300
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94107

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>doc4.xml
<DESCRIPTION>FORM 4 SUBMISSION
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-02-14</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001769490</rptOwnerCik>
            <rptOwnerName>Bergman Artur</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>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Architect, Exec. Chair</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-02-14</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>37914</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>351593</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-02-14</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>31413</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>383006</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-02-14</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4967</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>387973</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents the shares subject to performance-based restricted stock unit awards (PRSUs) earned based on the achievement of pre-established performance goals during the Issuer's fiscal year 2020. 25% of the number of PRSUs vested on February 15, 2021 and 25% of the number of PRSUs vest on May 15, 2021, August 15, 2021, and November 15, 2021, respectively, in each case subject to the Reporting Person's continued service with the Issuer through each applicable vesting date.</footnote>
        <footnote id="F2">The shares are represented by restricted stock units (RSUs). Each RSU represents a contingent right to receive one share of the Issuer's Class A Common Stock upon settlement. 100% of the RSUs are initially subject to vesting.  12.5% of the total RSUs vest on August 15, 2021, with the remainder vesting in 14 equal quarterly installments (November, February, May and August) of 6.25% thereafter, in each case subject to the Reporting Person's continued service with the Issuer through each applicable vesting date.</footnote>
        <footnote id="F3">The shares are represented by RSUs. Each RSU represents a contingent right to receive one share of the Issuer's Class A Common Stock upon settlement. 100% of the RSUs are initially subject to vesting. 25% of the number of RSUs vested on February 15, 2021 and 25% of the number of RSUs vest on May 15, 2021, August 15, 2021, and November 15, 2021, respectively, in each case subject to the Reporting Person's continued service with the Issuer through each applicable vesting date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Seth Gottlieb, Attorney-in-Fact</signatureName>
        <signatureDate>2021-02-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
