firefox performance
and choose Preferences. In the General panel, go down to the Performance section and uncheck the box next to Use recommended performance settings. You will then be able to change the following settings:

• Use hardware acceleration when available: This allows Firefox to use your computer’s graphics processor, if possible, instead of the main processor, to display graphics-heavy web content such as videos or games. This frees up resources on your computer so it can run other applications, like Firefox, faster. This box is checked by default but the feature isn’t available for all graphics processors. You must restart Firefox after changing this setting, before it will take effect.
• Content process limit: With Multiprocess Firefox, also called electrolysis or e10s , Firefox runs web content for all tabs separately from the main Firefox process for increased security and performance. Using multiple content processes can further increase performance and minimize the impact of content process crashes. You can modify this setting if multiprocess is enabled; however, having too many content processes can slow down your computer, and consequently, Firefox. The recommended maximum is four, but you can set up to seven.

about:memory
https://developer.mozilla.org/fr/docs/Performance/about:memory
id add-ons : about:support

Corrupt content-prefs.sqlite file

Firefox stores your data in various files in your profile folder. The file used for saving individual website settings might be corrupt. If you delete that file, your zoom level settings will be reset, but it should decrease CPU usage.

1. Click the menu button , click Help and select Troubleshooting Information. The Troubleshooting Information tab will open.
   • Under the Application Basics section, click on Open Directory. Your profile folder will open.

In your profile folder, delete the file content-prefs.sqlite. It will be recreated next time you open Firefox.