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How to purge old about:config records from uninstalled extension?

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Is there any way to clean-up my Firefox configuration database (about:config) from old unused records?

I try many addons and custom settings, and after uninstalling addon - seems they kept his records in about:config database, so they stay unused.

I want to check and remove all garbage (old & unused settings) from about:config list after bulk uninstalling addons.

Is there any way to clean-up my Firefox configuration database (about:config) from old unused records? I try many addons and custom settings, and after uninstalling addon - seems they kept his records in about:config database, so they stay unused. I want to check and remove all garbage (old & unused settings) from about:config list after bulk uninstalling addons.

All Replies (8)

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Start your search here; eCleaner Note: Not compatible with Firefox Quantum

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FredMcD said

Start your search here; eCleaner Note: Not compatible with Firefox Quantum

Thanks, but the main problem is 'Not compatible with Firefox Quantum' so this extension not available via search. Is any alternative to cleanup config available for Firefox Quantum?

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FredMcD said

Start your search here
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You can reset user set (bold) via the right-click context menu to the default value. An alternative is to edit prefs.js with Firefox closed and remove related lines from the file.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

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cor-el said

You can reset user set (bold) via the right-click context menu to the default value.

The main problem is that I don't know which lines are not used at now by any extension, so I don't know what to delete (reset).

For understand this, we must analyze installed extensions and check all keys that they use (mention in code, or Firefox have info of key creator?), and make comparison with current list of keys. Also exclude default list of config params from Firefox.

Modified by Alexey Murz Korepov

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Profile : Make a new ...:

What's What in the Profile :

  • bookmarks and history: places.sqlite
  • bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
  • cookies.sqlite for the Cookies
  • formhistory.sqlite for saved autocomplete Form Data
  • logins.json (passwords) and key4.db (58+) or key3.db (57 and older) (decryption key) for Passwords saved in the Password Manager
  • if you only have key3.db then make sure to remove an existing key4.db
  • cert9.db (58+) or cert8.db (57 and older) for (intermediate) certificates stored in the Certificate Manager
  • if you only have cert8.db then make sure to remove an existing cert9.db
  • persdict.dat for words you added to the spelling checker dictionary
  • permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
  • sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)

Suggest Make a New Profile for testing purposes so not needing to do this again.

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Pkshadow said

Suggest Make a New Profile for testing purposes so not needing to do this again.

I want to cleanup only my prefs.js database. I use Firefox many years and prefs.js contain many garbage keys from uninstalled extensions, that is synced to new profiles via Firefox sync.

For example, I have uninstalled Tab Mix Plus extension long time ago. At now I remove my old profile, create fresh new Firefox profile, configure Firefox Sync to my account.

And after sync finished - I see 50+ keys like 'services.sync.prefs.sync.extensions.tabmix.altClickTab' in my prefs.js (about:config)! Extension is even not installed on this profile, but keys are stored and synced to my any Firefox instance!

Modified by Alexey Murz Korepov

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Use the Search line at the top of about:config to locate each occurrence of tabmix and then one at a time right-click each of those prefs and use Reset. When you restart Firefox all those prefs should be gone from about:config and from prefs.js; the prefs,js file shows the non-default settings that are in about:config, including those prefs which are added to Firefox by extensions (default to the extension or user set in the extension).

Another way is to Search for occurrences of extensions to get a listing of those prefs. Most old Legacy extensions used "extensions" in the pref name going back to the days of Firefox 3.5 or 3.6; before then it was hit or miss to ID extensions by the pref name.


Quite honestly though, you are doing yourself a disservice by not creating a new Profile periodically; like when Firefox receives massive changes, as with Firefox 4.0 (Blue Firefox button), Firefox 29.0 (Australis)', and Firefox 57 (Quantum).

Personally with the large numbers of extensions that I run, I have created mew Profiles far more frequently than that. The "trick" is learning which files each extension saves to the Firefox Profile and then copying those files forward to the newly created Profile as each of those extensions is installed. Unfortunately that was impossible with Quantum due to all the Legacy extensions disappearing and WebExtensions use basically a "clean sheet" for extension data storage - IMO.

And as Pkshadow mentioned here - https://support.mozilla.org/en-US/questions/1220434#answer-1119298 - the "standard" Firefox data files would be need to be copied into the new Profile, replacing those already in the new Profile.