Here is the Firefox bug tracking high CPU usage when playing video on Mac. If you can reproduce high CPU on Mac, please share your Firefox's about:support infor

Here is the Firefox bug tracking high CPU usage when playing video on Mac. If you can reproduce high CPU on Mac, please share your Firefox's about:support information in the bug! https://bugzilla.mozilla.org/show_bug.cgi?id=1418510 https://bugzilla.mozilla.org/show_bug.cgi?id=1418510 VP9 is disabled by default in Firefox on Mac because H.264 can be hardware-accelerated on Mac but VP9 can't. Firefox supports hardware accelerated VP9 on some Windows machines, though.