Sleep Mode is a good idea, don't get me wrong. I've use this extension for a very long time while on Windows and without any problems until now. A few weeks after switching to Kubuntu 23.04 and then to Fedora 38 later, Firefox began crashing almost immediately. Disabling all extensions and re-enabling them one by one in Safe Mode traced the cause of all Firefox-related crashes back to this Sleep Mode extension. Because of this, I cannot in good conscience recommend the Sleep Mode extension to anyone until this fatal bug has been fixed on Linux!

So far works okay. Has some bugs that need to be ironed out to make the experience smoother.

Would be nice if you could manually put a tab to sleep. Like if I accidently click on an older tab, a right click option to put it back to sleep immediately would be nice. I imagine that would be difficult to do since the tab is already open, so maybe it switches to the next active tab before it does that?

Also, it would be nice if you could edit the sleep duration without having to disable and restart it. Like if I have it set to "Immediately" and then switch to "15 minutes", hitting start won't update it. I have to hit "disable", which then awakes every single tab (and causes a slowdown), before hitting "start". Functionality that updates the timer duration without resetting everything would be nice.

EDIT: Updating the timer doesn't seem to work at all actually. The icon will say "15" for 15 minutes, and the tabs will sleep after 15 minutes, but if I click on one then leave, it immediately goes to sleep.

EDIT #2: It just keeps sleeping my tabs immediately after leaving. This is a deal-breaker if the timer doesn't work. Uninstalling addon for now, may come back in the future.