Hi, Tried to find the solution but the problem boggles me. I'm using the latest version of Firefox on Windows 10 (2004). Using one Windows session (let's call it WS1), my profiles (even new ones) are extremely slow, as if I had a really bad Internet connection (but responds well to typing or opening new tabs or operating in general, just slow navigation). I have a backup browser, Opera, that works just fine. On another Windows session (WS2), Firefox works just fine, even with the profiles from WS1. Safe mode doesn't resolve anything. It can't be a driver problem, as it's the same PC, shouldn't be a software problem, same reason, and both sessions are built pretty much the same way. I tried uninstalling Firefox, using Windows Disk Cleanup as per this solution https://support.mozilla.org/en-US/questions/1219670 then reinstalling it again and no change. I can't use the other Windows session as it's not mine, and I can't create a new one either. Any help is greatly appreciated. Edit: I was finally allowed a new Win session and the problem disappeared. Can't delete the question though.