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default theme incompatible with latest firefox version

  • 2 replies
  • 3 have this problem
  • 5 views
  • Last reply by cor-el

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I had a Firefox 29 installation on one of my laptops and I copied the profile folder to backup to a different laptop. The other laptop though had Firefox 12 on it so I just updated it, and although my newer add-ons from the backup are now compatible, I can't use the default theme. Instead it has this very basic theme that isn't the default. If I look in the appearance tab it says "Default is incompatible with Firefox 30.0." The theme is labeled "Default 29.0.1". How can I get it to install the default theme for the current version? Thanks.

I had a Firefox 29 installation on one of my laptops and I copied the profile folder to backup to a different laptop. The other laptop though had Firefox 12 on it so I just updated it, and although my newer add-ons from the backup are now compatible, I can't use the default theme. Instead it has this very basic theme that isn't the default. If I look in the appearance tab it says "Default is incompatible with Firefox 30.0." The theme is labeled "Default 29.0.1". How can I get it to install the default theme for the current version? Thanks.

All Replies (2)

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You should be able to just delete the theme that is not working. Does it not have a remove option ?

Note the true default theme does not exist normally in the extensions folder. The extensions are modifications.

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You can try to delete the compatibility.ini file and check for issues with the files that stores the prefs.

Delete a possible user.js file and numbered prefs-##.js files and rename (or delete) the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in the current Firefox release.


Do a clean reinstall and delete the Firefox program before (re)installing a fresh copy of the current Firefox release.

If possible uninstall your current Firefox version to cleanup the Windows registry and settings in security software.

  • Do NOT remove "personal data" when you uninstall your current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including data in profiles created by other Firefox versions.

Remove the Firefox program before installing that newly downloaded copy of the Firefox installer.

  • (32 bit Windows) "C:\Program Files\Mozilla Firefox\"
  • (64 bit Windows) "C:\Program Files (x86)\Mozilla Firefox\"

Your bookmarks and other personal data are stored in the Firefox profile folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.


Modified by cor-el