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

    <schemaVersion>X0303</schemaVersion>

    <documentType>5</documentType>

    <periodOfReport>2008-12-31</periodOfReport>

    <form3HoldingsReported>0</form3HoldingsReported>

    <form4TransactionsReported>1</form4TransactionsReported>

    <issuer>
        <issuerCik>0001407739</issuerCik>
        <issuerName>DUPONT FABROS TECHNOLOGY, INC.</issuerName>
        <issuerTradingSymbol>DFT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001415044</rptOwnerCik>
            <rptOwnerName>Fateh Hossein</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O DUPONT FABROS TECHNOLOGY, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>1212 NEW YORK AVENUE, NW, SUITE 900</rptOwnerStreet2>
            <rptOwnerCity>WASHINGTON</rptOwnerCity>
            <rptOwnerState>DC</rptOwnerState>
            <rptOwnerZipCode>20005</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>241877</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>OP Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-07-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness>
                <value>L</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>141250</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>141250</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6010993</value>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                    <footnoteId id="F7"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Held by Trust</value>
                    <footnoteId id="F8"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>OP Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-11-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F9"/>
            </transactionCoding>
            <transactionTimeliness>
                <value>L</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>215000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F4"/>
                    <footnoteId id="F9"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>215000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5795993</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Held by Trust</value>
                    <footnoteId id="F8"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>OP Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-11-12</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F10"/>
            </transactionCoding>
            <transactionTimeliness>
                <value>L</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>292000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F4"/>
                    <footnoteId id="F10"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>292000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5503993</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Held by Trust</value>
                    <footnoteId id="F8"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeHolding>
            <securityTitle>
                <value>LTIP Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F11"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F11"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F11"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>95239</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>95239</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">&quot;OP units&quot; represent limited partnership interests of DuPont Fabros Technology, L.P., a Maryland limited partnership (the &quot;OP&quot;), the operating partnership of DuPont Fabros Technology, Inc. (the &quot;Issuer&quot;), of which the Issuer is the sole general partner. OP units are redeemable twelve (12) months from the transaction date pursuant to which the OP units were issued for cash equal to the then-current market value of one share of the Issuer's common stock, or, at the election of the Issuer, an equal number of shares of the Issuer's common stock.</footnote>
        <footnote id="F2">The 141,250 OP units reported on this line were distributed from the Athenee GRAT u/t/a dated June 12, 2007, a grantor retained annuity trust (the &quot;Athenee Trust&quot;), to Mercer Interests LLC, of which an entity controlled by Mr. Fateh is the sole member (&quot;Mercer&quot;), in connection with an annual annuity payment that was made on July 25, 2008.</footnote>
        <footnote id="F3">All of these OP units are immediately redeemable (subject to certain limitations set forth in the agreement of limited partnership of the OP).  OP units have no expiration date.</footnote>
        <footnote id="F4">The OP units (other than the OP units received in the transaction described in Footnote 2 above) were originally received in exchange for the direct or indirect contribution to the OP of certain partnership, membership, or ownership interests in, or property of, certain partnerships or limited liability companies which own and manage, directly or indirectly, certain properties in Illinois, New Jersey, Virginia, and/or the District of Columbia, in connection with the Issuer's initial public offering, the value of which was $21.00 per OP unit based on the price of the common stock of the Issuer at the time of the Issuer's initial public offering.</footnote>
        <footnote id="F5">These 6,010,993 OP units are indirectly beneficially owned through Mercer.  These OP units are comprised of the following: (i) 3,805,030 OP units that, in Fateh's previous Form 4 reports, were reported as being included in 5,214,893 OP units owned by Mercer.  As a result of an administrative error, 1,409,863 of these 5,214,893 OP units were mistakenly reported to be beneficially owned by Mercer.  This error resulted in Mercer inadvertently over-stating its ownership by these 1,409,863 OP units; (ii) 40,425 OP units that, as a result of the same error discussed above, were not reported as being allocated to Mr. Fateh and, instead, were mistakenly reported as allocated to the Athenee Trust.  These 40,425 OP units were reported in the Athenee Trust's aggregate holdings in Mr. Fateh's previous Form 4 report;</footnote>
        <footnote id="F6">[Continuation of footnote 5] (iii) 2,024,286 OP units that, in Mr. Fateh's previous Form 4 reports, were reported as owned directly by him. On December 10, 2007, Mr. Fateh transferred these OP units to Mercer, and as a result, the nature of Mr. Fateh's beneficial ownership of these OP units changed from directly owned to indirectly owned; and (iv) the 141,250 OP units transferred to Mercer as described in Footnote 2.</footnote>
        <footnote id="F7">Mr. Fateh's aggregate holdings of OP units in this Form 5 do not include the following holdings that were previously reported as being owned by him: (i) 1,560,329 OP units held by the Athenee Trust, and (ii) 1,497,024 OP units held by the Pamalican Trust u/t/a dated November 17, 2006, a trust for the benefit of persons other than Mr. Fateh (the &quot;Pamalican Trust&quot;).  Upon further review and reassessment of his interests in such trusts, it has been determined that Mr. Fateh did not at any time beneficially own any OP units held by the Athenee Trust and the Pamalican Trust - This determination was based in part on the fact that Mr. Fateh is not the trustee of either trust and that the trusts are not revocable.  Accordingly, the OP units were erroneously included in Mr. Fateh's previously filed Form 4 reports as beneficially owned.  Mr. Fateh does not intend to report these OP units as beneficially owned in future Section 16 reports.</footnote>
        <footnote id="F8">These OP units are indirectly beneficially owned through Mercer.</footnote>
        <footnote id="F9">The 215,000 OP units reported on this line were transferred from Mercer to the Pamalican Trust in exchange for cash of equal value. The aggregate cash value was $502,025, determined by reference to the midpoint of the reported high and low price of the Issuer's common stock on the NYSE on November 10, 2008, which was $2.335.</footnote>
        <footnote id="F10">The 292,000 OP units reported on this line were transferred from Mercer to the Pamalican Trust in exchange for cash of equal value. The aggregate cash value was $500,780, determined by reference to the midpoint of the reported high and low price of the Issuer's common stock on the NYSE on November 12, 2008, which was $1.715.</footnote>
        <footnote id="F11">Represents units of partnership interest which are structured as profits interest (&quot;LTIP Units&quot;) in the OP.  Conditioned upon minimum allocations to the capital accounts of the LTIP Units for federal income tax purposes, each LTIP Unit may be converted, at the election of the holder, into one OP unit. Each of the OP units underlying these LTIP units may be converted on or after twelve (12) months from the date of issuance of such OP units (A) at the election of the OP unit holder, for cash equal to the fair market value of one (1) share of common stock of the Issuer, or (B) at the election of the issuer, in its capacity as general partner of the OP, one (1) share of common stock. The rights to convert the LTIP Units into OP units and redeem OP units do not have expiration dates. These 95,239 LTIP Units were granted as long-term retention awards pursuant to the issuer's 2007 Equity Compensation Plan and were fully vested on the date of grant.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Hossein Fateh</signatureName>
        <signatureDate>2009-04-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
