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Firefox extensions spiking CPU and hanging browser

  • 3 replies
  • 1 has this problem
  • Last reply by FredMcD

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Firefox extensions stopped working for me tonight. If I click on any in the toolbar the little triangle appears but not the extension's actual menu. And the browser is hanging, not loading anything.

Also there is a huge cpu spike for the WebExtensions process. If I kill it, suddenly the web pages that were hanging start to load.

I'm using Firefox 79.0 on Ubuntu.
Attached screenshots

All Replies (3)

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It’s possible that there is a problem with the file(s) that store the extensions registry.

Type about:support in the address bar and press enter.

Under the page logo on the left side, you will see Application Basics. Under this find Profile Folder. To its right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder

Linux: Under the page logo on the left side, you will see Application Basics. Under this find Profile Directory. To its right press the button Open Directory.

Delete all extensions* files and compatibility.ini in the Firefox profile folder to reset the extensions registry.

New files will be created when required.

After, restart Firefox.

See "Corrupt extension files":

+++++++++++++++++++++++++++ You will have to approve the updating one last time.


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Thanks for the pointer in the right direction. After doing what you recommended, though, I would fall back into the corrupted state whenever I installed uBlock Origin.

After doing a Firefox refresh, everything works.


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Well done. Contact uBlock support for more help. Please keep us posted.


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