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userChrome no longer recognized in 86.0.1

  • 5 replies
  • 1 has this problem
  • Last reply by Slouch

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After updating to Firefox 86.0.1, my userChrome.css (in chrome directory) is no longer recognized, and customizations are not applied.

It worked fine in the previous version.

What could be wrong?


All Replies (5)

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What was the previous Firefox version ?

An update from 85.0.2 or 86.0 to 86.0.1 shouldn't be such a big problem that everything stops working.

I assume you still use this same profile, did you check that Firefox didn't create a new profile ?

What kind of code re you using in your userChrome.css ?


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It happened when updating from 86.0 to 86.01.

The same profile caused a problem.

Now, a new profile was created because I held down Shift while launching Firefox and Refreshed Firfox.

After copying the chrome directory to the new profile directory, the css mods are still not being applied.

Firefox just crashed as well. Details are below.

AdapterDeviceID: 0x0221 AdapterDriverVersion: AdapterSubsysID: 167919f1 AdapterVendorID: 0x10de Add-ons:,,,,,,,,,, AvailablePageFile: 2882469888 AvailablePhysicalMemory: 942465024 AvailableVirtualMemory: 1423683584 BreakpadReserveAddress: 38076416 BreakpadReserveSize: 83886080 BuildID: 20210310152336 CPUMicrocodeVersion: 0x2e ContentSandboxCapable: 1 ContentSandboxLevel: 6 CrashTime: 1615589442 ...


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If you have submitted crash reports, please post the IDs of one or more recent crash reports that start with "bp-".

  • bp-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

You can find the report ID of recent crash reports on the "Help -> Troubleshooting Information" (about:support) page.

  • click the "All Crash Reports" button on this page to open the about:crashes page and see all crash reports.

Alternatively you can open about:crashes via the location/address bar.

See also:


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You can check this pref on the about:config page to enable userChrome.css and userContent.css in the chrome folder.

  • toolkit.legacyUserProfileCustomizations.stylesheets = true



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This pref fixed the css issue: toolkit.legacyUserProfileCustomizations.stylesheets = true Strange that it was turned off in this update when it had been on in all previous versions

Here are the crash reports...

bp-1fb5cc10-ef6d-4b26-9bef-3e2350210313 3/12/2021, 8:18 PM bp-a4637467-61f9-4834-b2cb-c03f20210313 3/12/2021, 8:18 PM bp-ecd3f03f-8dde-452f-8247-b59c50210313 3/12/2021, 8:18 PM bp-0cf059b7-5ac3-4a11-a76b-a33c30210313 3/12/2021, 8:18 PM bp-eedff776-5fb5-4a7d-9833-b9da80210313 3/12/2021, 8:18 PM bp-3d529c3d-90cd-4e18-a108-e142f0210313 3/12/2021, 8:18 PM bp-4bc91727-eb84-49fb-823f-423dd0210313 3/12/2021, 8:18 PM bp-6acd70e1-f301-480d-903f-0da5f0210313 3/12/2021, 8:18 PM bp-9089e089-654a-4582-9d2a-d7e810210313 3/12/2021, 8:18 PM bp-068145df-5d92-4483-ba84-38ef00210313 3/12/2021, 8:18 PM


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