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You may not have realised this until now but Mozilla Firefox has its own version of the Windows Registry, where all your preferences are stored. In the browser, it can be accessed by typing in the address bar about:config

Backup Firefox Preferences

But what, in the future, if you have to re-install Firefox from scratch? You may have spent a long time tweaking Firefox to get it the way you want it and if you subsequently lose all your preferences, then you would have to start again from the beginning. This would throw me into a fit of rage but I discovered recently there is a way to make a backup of your “about:config” preferences in case anything goes wrong.

Just navigate to your Firefox profile folder in your Windows Explorer. For me, it’s under

Documents and Settings -> Mozilla -> Firefox -> Profiles

However, it may be different for you, depending on how you installed Firefox on your system.


When you have located the profile, locate a file called prefs.js. This is the file containing all your settings and preferences. Just copy that file to somewhere safe such as a USB stick, a re-writable CD disk or even just another location on your PC. Remember to update this file on a regular basis with your latest settings.

If you subsequently lose your preferences on Firefox, just drag your copied prefs.js file back into the Firefox profile. Windows Explorer will tell you that a prefs.js file already exists and would you like to replace it with your copied file? Say yes and your preferences will be updated the way you want them again.

  1. MP
    March 27, 2008 at 11:14 am

    Does this method backup bookmarks as well?

    • Mark O'Neill
      March 27, 2008 at 1:57 pm

      No, it doesn't. To back up bookmarks, I suggest you use something like Foxmarks.

  2. mymytri
    January 21, 2008 at 5:40 am

    Good tip here.I use FEBE for fewdays and it works good till now.

  3. Fernando
    January 15, 2008 at 3:45 am

    Go up a couple levels. You should see a folder called profiles and a few other folders. These contain (to my knowledge) all your firefox extensions, etc. I tested it and it works like a charm. (I got another Windows account's firefox settings + extensions running.

  4. A Non
    January 14, 2008 at 9:27 pm

    Or you could use MozBackUp:

    • mark
      January 21, 2008 at 11:46 am

      I use this too. Never had a problem yet.

  5. הורדות לסלולרי
    January 12, 2008 at 6:45 pm

    interesting, thank for the info

  6. Mark O'Neill
    January 12, 2008 at 10:08 am

    My understanding of the prefs.js file is that it only records your preferences that you set in the Tools>Options menus. It also records any tweaks you may have made to the way Firefox accesses the internet, displays URL's, stores bookmarks and any other basic functions of the browser.

    To the best of my knowledge, it does NOT keep a record of your plug-ins and extensions. Those are recorded in other areas of your Firefox profile which can also be saved separately.

    • Chuck Baker
      January 13, 2008 at 7:28 am

      The prefs.js file DOES contain individual extension preferences (options). For instance, type "extensions.febe" into the filter box and you will see all FEBE preferences.

      There is a new Firefox add-on that will import/export individual extension preferences. It is called Ordered Preference Import/Export (OPIE).

  7. Ana E. Arrington
    January 12, 2008 at 10:06 am

    Why not use FEBE (Firefox Environment Backup Extension) instead? Can also backup preferences in addons...

    • Mark O'Neill
      January 12, 2008 at 10:12 am

      I have tried using FEBE in the past and it failed miserably to restore any of my Firefox profile (I lost a LOT of Firefox tweaks that day and it took me a long time to get Firefox back to the way I had it before).

      The problem with these Firefox backup programs is that you are totally dependent on these programs being continued and maintained by their developers. What if one day the FEBE developer suddenly decided not to continue supporting the program and shut the whole thing down? Your Firefox backups would be completely useless!

      That is why I prefer to shun these backup programs and instead manually backup the profile myself onto a USB stick or re-writable CD disk. I don't like to rely 100% on one program.

  8. kasperhors
    January 12, 2008 at 6:12 am

    Does it keep prefs for addons an plugins aswell? For example MouseGesture?

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