Hello marekzych90,

See Firefox uses too much memory or CPU resources - How to fix .

Hope it helps. Thank You.

Im sorry but no. I already restored default settings and it didn't work. I reinstalled firefox and it didn't work. If new installation does not work then i'm sorry i'm not going to do workaround for that. Also firefox lost connection and was not able to load any webpage - only system restart worked but at the same time chrome didn't have this problem. All happened after upgrading to version 77. Does new version got tested before release? Im dissapointed because i was using firefox for over 10 years now and this update ruined everything.

Historically, high CPU usage with videos has been associated with Google's VP9 encoding, which for some reason Firefox wasn't able to offload to the GPU.

I haven't noticed any change with Firefox 77, but I tend to watch pretty standard videos, no 4K, no 60fps.

I was watching quite standard 720p video. I noticed significant degradation is speed in v77. All pages have few seconds lag before they load (i have ssd and a lot of free space). The problem does not occur on chrome and didn't occured on v76 so the problem is new version. v77 after updating was not able to load any page (except google.com - seems like speed was in kb/s) until i restarted the system. I don't have any external antivirus/anti-malware that could cause issue. I switched to chrome and i don't have any of mentioned issues so the problem is caused only by new version.

hello marekzych90

This is very common issue please follow the link resolve your prolmem easily :

Uninstall Firefox from your computer:

[https://support.mozilla.org/en-US/kb/uninstall-firefox-from-your-computer...]

download and install Firefox:

[https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-win...]

i have resolve your problem then reply back to me.

thank you