Hi florian2833z, Safe Mode also temporarily disables hardware acceleration.

Check that your graphics driver is up to date and/or disable hardware acceleration in your Options -> General page -> Performance section. Uncheck Use recommended performance settings and you'll see Use hardware acceleration when available.

Hey,

Thanks for the quick reply. Unfortunately, this does not fix the high cpu usage. Is there anything else that is changed when using safe mode?

I think the only other settings which are changed in Safe Mode are for Themes and turning off your bookmarks toolbar.

When you started Firefox normally, then disabled your extensions, it could still be an extension causing the problem.

Try disabling all of your extensions, then Close Firefox. Start Firefox again normally and see if the problem persists.

If it works OK then, it's probably a faulty extension. Enable your extensions one-at-a-time to see which one is causing the problem.

Firefox also has a built-in Task Manager which might help you determine a faulty add-on.

Click on the 3-bar Menu button Select More Select Task Manager

or type about:performance in the address bar and press enter.

You can try to disable VP9 via the about:config page.

• media.wmf.vp9.enabled = false

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

cor-el said

You can try to disable VP9 via the about:config page.

• media.wmf.vp9.enabled = false

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Thank you for this info, I disabled vp9 via config, restartet firefox and still youtube shows vp9 as currently used codec. Is this a bug?

My_Cheese_Is_Slippin' said

Firefox also has a built-in Task Manager which might help you determine a faulty add-on. Click on the 3-bar Menu button Select More Select Task Manager or type about:performance in the address bar and press enter.

I already tried the taskmanager, but it doesn't show cpu usage per tab or addon, at least I haven't found it yet. It only shows how much power is used by tab and weirdly it says that youtube consumes "medium" energy, although CPU is up to 50%.

My_Cheese_Is_Slippin' said

I think the only other settings which are changed in Safe Mode are for Themes and turning off your bookmarks toolbar. When you started Firefox normally, then disabled your extensions, it could still be an extension causing the problem. Try disabling all of your extensions, then Close Firefox. Start Firefox again normally and see if the problem persists. If it works OK then, it's probably a faulty extension. Enable your extensions one-at-a-time to see which one is causing the problem.

Ha, you were right! I had to disable Stylus (https://addons.mozilla.org/en-US/firefox/addon/styl-us/) and then restart Firefox and that did the trick! My CPU is not at 50% all the time anymore, thank you. What I don't understand tho is why Stylus is a recommended addon. I guess it's only my setup (stlyes) or something like that.

florian2833z said

My_Cheese_Is_Slippin' said

I think the only other settings which are changed in Safe Mode are for Themes and turning off your bookmarks toolbar. When you started Firefox normally, then disabled your extensions, it could still be an extension causing the problem. Try disabling all of your extensions, then Close Firefox. Start Firefox again normally and see if the problem persists. If it works OK then, it's probably a faulty extension. Enable your extensions one-at-a-time to see which one is causing the problem.

Ha, you were right! I had to disable Stylus (https://addons.mozilla.org/en-US/firefox/addon/styl-us/) and then restart Firefox and that did the trick! My CPU is not at 50% all the time anymore, thank you. What I don't understand tho is why Stylus is a recommended addon. I guess it's only my setup (stlyes) or something like that.

Specifically, it was this certain style: https://userstyles.org/styles/164882/rainbowtube

Problem solved!

Great! I'm glad to hear that you got the problem solved. Now, you can binge-watch on Youtube!

FYI: The recommendation for the extension comes from reviewers at AMO. Evidently their criteria doesn't include thoroughly checking out each and every style.

My_Cheese_Is_Slippin' said

Great! I'm glad to hear that you got the problem solved. Now, you can binge-watch on Youtube! FYI: The recommendation for the extension comes from reviewers at AMO. Evidently their criteria doesn't include thoroughly checking out each and every style.

Of course, they can't check every single style that exists haha Thanks for your help!