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I have a Ubuntu (Unity) 22.04.4 LTS (Jammy Jellyfish) installation which distributes firefox via snap.

The problem im facing is, that whatever changes i made in about:config, after a restart of firefox the changes i made are gone.

For example, i disabled the tab preview (browser.tabs.hoverPreview.enabled): enter image description here

After closing, and opening firefox, the value is again "true".

Is this a bug in firefox or a problem with snap?

spikey_richie
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Marc
  • 529

3 Answers3

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I had the same problem, and it turned out my browser had a study turned on for the feature that overrode the about:config setting.

If the same is the case for you you can go to about:studies and remove Tab Hover Preview Release Rollout.

Martin Brenden
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First what comes to mind is that you have permissions issue - I just tested "browser.tabs.hoverPreview.enabled" on my FF (Rocky 8.10 not Ubuntu though) - it's not a protected preference, I succesfuly changed it back and forth a few times.

My advice:

  1. Go to about:profiles, open "Root directory" of your active profile and check your writing privileges for it, including all the files and directory itself. Most important in your case would be prefs.js file.

  2. Open the file and look for browser.tabs.hoverPreview.enabled. Here's how it looks in my file:
    example

  3. If you can't see obvious privileges problem try adding the entry manually (with FF closed!), save, check FF, close, change the value in file, check FF.


If this doesn't help check if any of the following exists:

  1. %Firefox installation directory%/distribution/policies.json
    Documentation
  2. %Firefox installation directory%/firefox.cfg and defaults/pref/autoconfig.js Documentation
  3. %active FF profile directory%/user.js

If any one of those exists - it overrides prefs.js

mrd83
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0

I had the same issue. I've totally re-install firefox last week due to this, but the issue came back when modifying other pref in about:config. I've been keeping user.js and pref.js "under surveillance" for the past month (text editor) and it kept alerting that the files were changed. I found many treads about this but I'm not looking for 6yrs old issues. After investigating the profile directory I found a never seen before file: "Invalidprefs.js". I decided to delete that file an hour ago and check to see if it came back by itself (close firefox restart etc several times) and the issue has not come back, til now.

I also, maybe not needed, made the "pref.js" as read-only. But I'm sure I'll have to save both user.js and pref.js on the next firefox update/upgrade.

I've not tried yet on Arch/Debian not win11 (vBox). I'm on win10 firefox 136.02

edit: Maybe I should include this:

There's a hidden pref in about:config

I had added this line in both user.js and pref.js since version 128.

user_pref("dom.private-attribution.submission.enabled", false);

It was, and still is, in none of the file. It is suppose to appear in the setting page, but not. Once you put this "browser.urlbar.update2.engineAliasRefresh" in about:config you'll see it, and set to "true". Only once you set it to "false", it will appear in the privacy-setting page and unchecked. This means that while it is invisible it is set to "true".

Ghis1964
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