Huh. Doesn't happen to me. I'd suggest using about:memory to see if you have a leaky tab. In my case, it used to be that my FB and Twitter tabs both leaked a lot. I stopped leaving Twitter open and FB (or Firefox) seems to have fixed their problem.
Yeah, I tried that. the about:memory usage reported is much lower (and strikes me as more reasonable).
I use an unload tab extension so currently there should be no 'open' tabs. Memory usage is at 1.5Gb though. It doesn't seem to go much higher or lower, though, so could it be that FF just takes/keeps the RAM it can get and doesn't bother to unload stuff?
It's also true that my MacBook has become slower in general since I updated to the latest MacOS, so perhaps it's not FF fault. Still, very annoying.
