I have an existing installation of Firefox. I've been using this installation for a long time so theres a lot of data (history, bookmark, browser preferences, addon preferences).

Now I want to split this data (browser history, bookmarks, some settings) with the result that some data is only accessable by instance #1 and the other data is only accessable by instance #2. I know that I have to delete most unwanted data manually but thats ok.

My first thought was to clone the profile but I figured out that there are many spots where the actual profile name is hardcoded. The second possibility I see is that I add another installation of the same Firefox version to my system and transfer the profile to the new installation.

Is there a way to do that? Or is there an alternative solution?

  • You want to have some files shared between profiles, permanently, with the data stored in the same folder, or you want two profiles forked from your original one?
    – dr.nixon
    Commented Feb 27, 2014 at 15:34
  • I want two forks of the original profile.
    – Noir
    Commented Feb 27, 2014 at 21:11

2 Answers 2


Your question is asking for something technically possible, in that it may be possble to "split" data in your profile, and distribute it among other profiles, but it sounds incredibly difficult to do considering what you would you gain doing this manually, as opposed to simply setting up new profiles and entering the data you wish into each new profile, and deleting the data from the other profile.

To accomplish everything you're asking for (except this splitting of the original profile data) is largely academic. The basic idea is have multiple profiles, and have multiple instances of Firefox each accessing a different profile. The way you do that is you first set up the multiple profiles, and you can do this by accessing the Profile Manager. Open your /Applications/Utilities/Terminal.app and type this at the command prompt:

 /Applications/Firefox.app/Contents/MacOS/firefox-bin -profilemanager &

and the window that appears, along with information at the link provided above, will get you started on creating the extra profiles. Once these profiles are created, you can start the first instance of Firefox by clicking the Start Firefox button, and you can then launch your subsequent instances of Firefox using that same command. Again, in Terminal.app type the following:

 /Applications/Firefox.app/Contents/MacOS/firefox-bin -profilemanager &

and you will see a second instance of Firefox appear in your dock. Choose the profile you wish for the second Firefox instance, and click Start Firefox. Repeat these steps (pressing the up arrow will display the last command) for as many instances of Firefox that you wish to run, or until you run out of memory.


I know this is an old question but it deserves an answer. Since Apple introduced Mavericks they managed to break the ability of running multiple copies of Firefox side by side. I used to have this working on Lion perfectly and since Mavericks it will not work as it's impossible to launch the same application more than once. I spent nearly 5 days on El-Capitan figuring this out as no tutorials out there worked at all and I found a solution that works for me and I am using it everyday running 4 copies of Firefox side by side, each with their own profile, own plugins and they all update separately from each other. My solution will work on Mavericks, Yosemite, El-Capitan and also Sierra which is what I am running on now.

  • Sorry but being a new user on this group I am unable to comment only reply. All the stack groups work that way. I spent days finding that solution and believe it does answer the question the OP asked. (and now first time I ever I joined a new stack group and I can post a comment ... so I take that back)
    – MitchellK
    Commented Feb 6, 2017 at 13:54
  • 2
    You can remove the comment to me from your answer. Also, we prefer all answers be self-contained, according to How to Answer, so please post your answer here instead of linking to it.
    – fsb
    Commented Feb 6, 2017 at 14:24
  • 1
    Please include the solution directly into your answer, not only a link (which may break sooner or later) to an external site. This will greatly increase the value of your answer which probably will lead to upvotes (and more rep points for you).
    – nohillside
    Commented Feb 6, 2017 at 14:27
  • As for comments, you can always comment on your own posts, but you need a certain level of reputation to comment on posts made by others. See the FAQ for details on how the SO sites work.
    – nohillside
    Commented Feb 6, 2017 at 14:28
  • Thanks, I understand that now and see I was indeed allowed to comment on my own reply. Have good reputation on other stack groups and having to earn them all over again on new one's takes time. Unfortunately such a long solution and lots of images and screen grabs posting it here would be a nightmare but I can try.
    – MitchellK
    Commented Feb 6, 2017 at 15:12

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