Your useragent used to post this thread appears as Mozilla/5.0 (Windows '''NT 6.0'''; Win64; x64; rv:'''109.0''') Gecko/20100101 Firefox/115.0 NT 6.0 is Windows Vista as Windows 7 is NT 6.1 https://en.wikipedia.org/wiki/Windows_NT Perhaps you are running Firefox 115 in Windows Vista compatibility mode on Windows 11 or you have a modifies UA for some reason. https://support.mozilla.org/en-US/kb/how-reset-default-user-agent-firefox Though It does appear to be modified UA as the Gecko rv: should be the same as the Firefox version and not 109.0 The proper Firefox 115 useragent on Windows 11 should show as Mozilla/5.0 (Windows '''NT 10.0'''; Win64; x64; rv:'''115.0''') Gecko/20100101 Firefox/115.0 Windows 11 is based on same kernel as Windows 10 so it would still be NT 10.0 Also try downloading the full offline setup instead of the small online stub installer. https://www.mozilla.org/firefox/all/