chris600 said

okay so the cpu usage spikes alot when i am not doing anything but when i watch youtube videos it sometimes spikes up to 70 but mostly in the 50s

Please see: Firefox uses too many CPU resources - How to fix

You can try to disable hardware acceleration in Firefox.

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"

You need to close and restart Firefox after toggling this setting.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can check if there is an update for your graphics display driver and check for hardware acceleration related issues.

• https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

I have done all the suggested things to reduce FF CPU usage, and none of it works. FF is just too bloated! It's always using 100+ of my CPU, causing my fan to be on all the time (MacBook Air 2012), even when in the background.

Only when I quit FF does my fan turn off.

Mozilla really needs to rewrite this thing from scratch.