Huh! I wouldn't expect that at all... here are some easy things to try:

https://support.mozilla.org/en-US/kb/firefox-uses-too-many-c...

If it is still happening after you try those, use https://perf-html.io/ and share a profile.

Known bug, I think, assuming you've enabled webrender. They're still working on correctness. They haven't gotten to optimization yet.

Also nightly contains all sorts of debug stuff

only two webrender about:config entries are true

I'll see how it goes with the normal release

If you want to know for sure if Webrender is enabled you can go to about:config and check the Graphics section. If Compositing is 'Webrender' it's turned on.

all I can see is skia

Are you on a Mac by any chance?

Funny you mention this. While Firefox’s interactive performance on Mac feels absolutely fine, it’s energy consumption is dramatically worse compared to Safari.

Using Firefox over Safari can cost hours of battery life, so it’s very hard to recommend it. Is this just a Mac issue?

I know of one issue with Firefox when you are using a scaled resolution. It absolutely destroys battery and performance for me. I _think_ it has gotten better with the latest versions but the tickets are still open.

https://bugzilla.mozilla.org/show_bug.cgi?format=default&id=...

https://bugzilla.mozilla.org/show_bug.cgi?id=1407536

https://news.ycombinator.com/item?id=17365510

thinkpad, old i5, archlinux