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        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001508655</identifier>
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        <period>
            <startDate>2025-01-01</startDate>
            <endDate>2025-12-31</endDate>
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    <dei:DocumentType contextRef="P01_01_2025To12_31_2025" id="hidden160238254">DEF 14A</dei:DocumentType>
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    <dei:EntityCentralIndexKey contextRef="P01_01_2025To12_31_2025" id="ixv-2857">0001508655</dei:EntityCentralIndexKey>
    <dei:EntityRegistrantName contextRef="P01_01_2025To12_31_2025" id="ixv-2867">Sixth Street Specialty Lending, Inc.</dei:EntityRegistrantName>
    <ecd:InsiderTrdPoliciesProcAdoptedFlag contextRef="P01_01_2025To12_31_2025" id="ixv-2871">true</ecd:InsiderTrdPoliciesProcAdoptedFlag>
    <ecd:AwardTmgMnpiDiscTextBlock contextRef="P01_01_2025To12_31_2025" id="ixv-2234">&lt;div style="margin-top:0pt; margin-bottom:0pt; margin-left:4%; font-size:10pt; font-family:Times New Roman;font-weight:bold"&gt;&lt;div style="font-style:italic;display:inline;"&gt;Policies and Practices Related to the Timing of Equity Awards &lt;/div&gt;&lt;/div&gt;&lt;div style="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"&gt;The Company does not grant options, and accordingly, we have no policy, program, practice, or plan pertaining to the timing of stock option grants with respect to the release of material &lt;div style="white-space:nowrap;display:inline;"&gt;non-public&lt;/div&gt; information. Furthermore, given that we do not directly compensate our executive officers, we also have not timed the release of material &lt;div style="white-space:nowrap;display:inline;"&gt;non-public&lt;/div&gt; information for the purpose of affecting the value of executive compensation. &lt;/div&gt;</ecd:AwardTmgMnpiDiscTextBlock>
    <ecd:AwardTmgMethodTextBlock contextRef="P01_01_2025To12_31_2025" id="ixv-2238">The Company does not grant options, and accordingly, we have no policy, program, practice, or plan pertaining to the timing of stock option grants with respect to the release of material &lt;div style="white-space:nowrap;display:inline;"&gt;non-public&lt;/div&gt; information.</ecd:AwardTmgMethodTextBlock>
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