Easily Backup Mozilla Firefox “about:config” Settings

If you want to tweak Mozilla Firefox to the extreme, then about:config is where you should look out for all the advanced settings. But tweaking about:config without any knowledge of what the settings does, may be very harmful for Firefox’s health. So it would be a good idea to backup about:config first. This backup will help you very much. Even if anything goes out of your hands. You can easily restore everything back to normal.
It’s also a good idea to backup about:config if you have customized Firefox a lot. So, the next time you reinstall Firefox, you can replace the default settings with your customized one.

How to backup about:config settings in Windows Vista or Windows 7?

Here is how you can easily backup the about:config settings and save yourself some trouble.

1. First and foremost, if Mozilla Firefox is running, exit it.
2. Click on the Start button. Click on Run… Alternatively, you can press the Windows + R keyboard shortcut.
3. Type %appdata%\mozilla\firefox\Profiles and click on OK or press Enter.

4. In the window that opens, you will see your Firefox profile folder: <some random characters>.default, e.g. l4aknmw.default.
5. Open the folder and search for a file called prefs.js. This is the file which has all about:config settings.

6. Back up this file to a safe place.
7. Now, you can safely change Firefox about:config settings. If you mess up something or Firefox behaves odd, simply close down Firefox and replace the existing prefs.js file with the backup file.

How to backup about:config settings in Windows XP?

Just follow the above steps. Simply look for your Firefox profile in \Documents and Settings\<YourUsername>\Application Data\Mozilla\Firefox\Profiles\

How to backup about:config settings in Mac OS X

You will find your Firefox profile at <YourUsername>/Library/Application Support/Firefox/Profiles. Open your Firefox profile folder <some random characters>.default and keep a backup of prefs.js to a safe place.

How to backup about:config settings in Linux

Linux users will find their Firefox profile at ~/.mozilla/firefox/. You’ll find your profile folder named <some random characters>.default. Open it and copy the prefs.js to a safe place.
 
Warning! Always shut down Firefox before making a copy of prefs.js or moving a copy back into the profile folder.

source: http://www.mytechguide.org/97/easily-backup-aboutconfig-firefox/