Firefox since Fx 116.0 and later including the current Firefox 131.0 release is for Windows 10 and 11 as Windows 7, 8, 8.1 is no longer supported on new releases since (though they are still supported with Fx 115 ESR). There is no version of Firefox only for Windows 10 and Firefox only for Windows 11. How do you figure that you installed Firefox for Windows 10? In your More System Details on right your UserAgent is Mozilla/5.0 (Windows '''NT 10.0'''; Win64; x64; rv:131.0) Gecko/20100101 Firefox/131.0 The UA will show NT 10.0 even if you have Firefox installed on Windows 11 both because it shows NT 10.0 since the Firefox 116.0 Release and because Windows 11 is based on the same NT 10.0 as Windows 10. Also https://www.mozilla.org/firefox/131.0/system-requirements/ Windows Operating Systems (32-bit and 64-bit) Windows 10 or later