Hello, all. For years now, I've been facing the same issue and it is: Firefox breaksdown and becomes chaos during every update. What do I mean by 'during every update'?. I'll explain how I use firefox and what happens. I am writing code that is tracking data from a websocket connection. That's why I leave Firefox open all the time, just for tests, to see how my web app would react to different situations. At some there is a Firefox Update. It downloads and installs it, but never actually notifies me when anything of that is happening. Here is the magic - I always know when there was a new version just installed. How? Firefox performance drops, weird and unexpected behaviour and it just becomes chaotic and sluggish until I restart. so I was looking at the console logs of the app that I am developing and after. All of a sudden, I start getting a "SyntaxError: redeclaration of let settings" or something like that (wish I had saved it). The error did not come from my code as I haven't use any 'lets' in my JS code. That SyntaxError was quite specific and I just noticed it in the last update, but the performance drop issue has been there for years now. Maybe that syntaxError was not specific to my app, but on a lower level. I have to keep observing, but I wanted to report it here. Every time there is an update (not a specific one) and I'm using firefox at the same time - I instantly notice the difference. I know, all I need to do is restart the browser and it works fine, but do we really want our browser to behave like that? Do we really want our work to be interrupted by an update that can wait until I restarted my PC? Windows 10 has the same issue. "I DON'T CARE WHAT YOU ARE DOING OR HOW IMPORTANT YOUR STUFF TO YOU IS! HERE IS AN UPDATE THAT WILL BREAK EVERYTHING AND YOU ARE FORCED TO RESTART". I know, I should review my firefox update settings, but these are the default firefox settings firefox comes with and it happens even on a clean install. There are people who would be like... *getting my werid acting voice out* "Oh, this browser has become so slow all of a sudden. Let me try Chrome. OMG! YES! IT'S FASTER!! I'll stick to that". I did not keep any other issue, since i just closed the browser and did not bother to open it again. I opened it this morning and there was little update window. That makes me think now.. Does the update installation happen before I restart the browser or after? If the installation happens after the browser is clsoed, that would mean just the download itself breaks the browser. I have a few addons active, but as I mentioned earlier, this happens even when there is an update after a clean install. Thanks for your time reading this. when I this happens again, I will try to gather more data and will update or post a comment under this post. Can anyone suggest any good way to pinpoint the cause? Thanks!