I installed Firefox on a Macbook Pro with Apple Silicon, M3. The installation was from the Firefox site, I downloaded the dmg and then dragged into Applications. I find that playback of media stutters, and is choppy--not sure of a better way to explain it. E.g., YouTube videos and the Bandcamp player have "stuttered sound". Opening another site in another tab can make this effect worse. Likewise, trying to run Google Meet in a browser window causes basically everything on the computer to become very slow. This still happens even if I go to "about:profiles" and then "restart with add-ons disabled". But if I switch to another browser, Safari or Chrome, then I don't have the issue. e.g. I can play YouTube in the background fine even when running some compute intensive task. I have also tried turning on/off "performance settings" and the "use hardware acceleration" checkbox underneath it -- neither of those seem to have any effect. Activity Monitor showed that at most Firefox was using ~4 GB of memory of a total 48 GB, and the memory pressure indicator seems to be quite low. I have run Firefox on other systems (e.g. System76, older Macbook Pro) with multiple windows open each having 20-30 tabs and never had an issue like this. It really seems like it has something to do with how Firefox is interacting with the M3? Happy to learn I'm wrong. And happy to provide more details about the hardware or my settings if it would help.