Firefox occasionally resets all preferences.
My Firefox resets all the preferences if there has been some time since I have previously opened the browser. If I keep closing and opening the browser, it works fine, nothing resets. But lets say if I close the browser and come back in an hour and open it again I get the "firstrun" page and all my plugins are disabled. Same happens if I for example turn off the PC overnight and come back in the morning and open the Firefox. If I turn off the PC and shortly turn it back up again everything works. But it doesn't happen 100% of the time. Longest I have gone without a reset is approximately 12hours.
I have tried every guide on the internet and tried every step of this guide https://support.mozilla.org/fi/kb/how-to-fix-preferences-wont-save but it still won't work.
I have checked all my preference files and they are not Read-Only. I have CCleaner installed, but running it doesn't reset the preferences. I have tried to force the CCleaner to reset the preferences, but no matter how hard I try to reproduce the issue I can't.
Chosen solution
You lose the preferences if Firefox isn't able to create a new prefs.js file in the Firefox profile folder.
Is there only one prefs.js file in the Firefox profile folder or do you have any numbered temporary prefs-##.js files?
Did you try to delete all prefs.js files in the Firefox profile folder?
Delete possible user.js and numbered prefs-##.js files and rename/remove 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 current Firefox releases.
You can try to create a new profile to test if your current profile is causing the problem.
See "Creating a profile":
- https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
- http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues
If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.
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After not getting any answers here I thought to take the matter in my own hands. I uninstalled all the programs that could have caused this, everything down to the F-Secure SAFE. I removed all the add-ons and did a fresh install of Firefox and kept it that way. But none of that helped. I have 3 PCs that have exactly the same software on all of them down to the version number and only my Desktop PC has this issue. I have even used Microsoft's Process Monitor to see if any other programs access prefs.js file or any other file in my profile folder with negative results. Firefox is the only process that accesses them.
As much as I hate using Chrome, that might be my only option here if I don't resolve this.
Note: Some software, like Advanced SystemCare with Surfing Protection, can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.
If the above does not help,
Start your Computer in safe mode with networking. Then start Firefox. Try Safe websites. Close Firefox
Wait 1-2 hours. then start Firefox again. Is the problem still there?
Chosen Solution
You lose the preferences if Firefox isn't able to create a new prefs.js file in the Firefox profile folder.
Is there only one prefs.js file in the Firefox profile folder or do you have any numbered temporary prefs-##.js files?
Did you try to delete all prefs.js files in the Firefox profile folder?
Delete possible user.js and numbered prefs-##.js files and rename/remove 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 current Firefox releases.
You can try to create a new profile to test if your current profile is causing the problem.
See "Creating a profile":
- https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
- http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues
If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.
Modified by cor-el
Only deleting current profile and creating a new one helped. Thanks!