This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Avatar for Username

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

This thread was archived. Please ask a new question if you need help.

Firefox CPU usage increases dramatically while playing YouTube videos full-screen

  • 1 reply
  • 1 has this problem
  • 7 views
  • Last reply by TyDraniu

Giulia
Giulia
more options

I'm using Firefox v 83.0 on Manjaro (Gnome) Linux. YouTube videos in theater/full-screen mode lag if resolution is higher than 360p and cause the CPU usage to burst. This happens for large web pages as well: when I scroll the page, text overlaps and everything is terribly slow. I've checked and this seems to be a Firefox related problem; videos play smoothly both on VLC and Chromium. I've tried all official troubleshooting suggestions: changing to default theme, refreshing Firefox, starting in safe-mode, disabling extensions, disabling hardware acceleration and so on, with no success. I've never had any problems with Firefox for Linux before and I wonder what could be the cause.

I attached screenshots for comparison of CPU usage for the same video playing in theater mode in Firefox and Chromium.

I'm using Firefox v 83.0 on Manjaro (Gnome) Linux. YouTube videos in theater/full-screen mode lag if resolution is higher than 360p and cause the CPU usage to burst. This happens for large web pages as well: when I scroll the page, text overlaps and everything is terribly slow. I've checked and this seems to be a Firefox related problem; videos play smoothly both on VLC and Chromium. I've tried all official troubleshooting suggestions: changing to default theme, refreshing Firefox, starting in safe-mode, disabling extensions, disabling hardware acceleration and so on, with no success. I've never had any problems with Firefox for Linux before and I wonder what could be the cause. I attached screenshots for comparison of CPU usage for the same video playing in theater mode in Firefox and Chromium.
Attached screenshots

All Replies (1)

TyDraniu
TyDraniu
  • Top 10 Contributor
more options

This error message is suspicious: "Acceleration blocked by platform". Your Firefox doesn't use GPU.

Try to enter about:config and set layers.acceleration.force-enabled = true, then restart the browser.