How to run Firefox 3 and Firefox 4 simultaneously in Windows

Most of us have upgraded to the latest version of Firefox, that is the Firefox 4 Beta which works exceedingly well and is quite a stable build. However, some people are facing problems while running their favorite add-ons on the latest offering from Firefox.

Those who want to get the best of both worlds can try and run Firefox 3 build, along with the Firefox 4 beta version simultaneously. If you try and run both the versions simultaneously it wont work because by default both of the versions will try and run on the same profile and resulting into the working of only one of the versions. But you can do a small modification to the profiles, you will be able to use both of the versions simultaneously.

Here’s how it works:

  • There is by default only one profile for the Firefox,so you have to create one more profile to make this work.
  • Hit Windows+R and type “/path/to/firefox -P profile_name -no-remote" in the box and Hit Enter.
  • Now a profile manager will be opened click on Create profile

  • Proceed to the next step by clicking next

  • Enter a Name for the profile and the default path will be chosen for saving the profile and if you want you can select a custom path as well.

  • Hit finish to complete the Profile Creation process.

  • Select the new profile and click Start Firefox. Now you can run both the versions of Firefox simultaneously.

That’s it!

UPDATE by Admin: Our TWC Forum thread The “EASY” way to use both Firefox 3 & 4, and easily switch between them may also interest you.

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The author is a MVP Alumni, pursuing his Computer Engineering Degree. A tech enthusiast, he blogs everything about Microsoft at You can follow him @Sagarsaw on Twitter.


  1. Navjot Singh

    This tip is incomplete. Even if you create a new profile, you still can’t run both firefox versions simultaenously cause both versions will start using the newly created profile. You will also need to create a shortcut to Minefield browser with the newly created profile in this way: “C:Program FilesMinefieldfirefox.exe” -P -no-remote

    and then run Minefield (Firefox 4 beta) with this shortcut and Firefox 3 with the old profile. Only then you can run both versions simultaneously.

  2. Navjot Singh

    Oops…link to shortcut got cut it is again: “C:Program FilesMinefieldfirefox.exe” -P Profilename -no-remote

  3. BlackWitch

    I think I believe Navjot. I had to return Firefox3 to Default User Profile to regain my Bookmarks and Settings.

    But I do not seem to get the link to Firefox4

  4. BlackWitch

    Oops…addons do not still work. How do I remove Firefox4 already in that Default Profile, as I link it to the new Profile.

  5. Sagar

    Sorry guys, I forgot to add the rest of the tip. You can checkout the solution by our TWC forum member:

  6. BlackWitch

    I tried the EASY way, got F3 & F4 running side-by-side. But my Bookmark & customisations were gone. It was rather a new installs.

    Where did I get it wrong?

  7. Sagar

    @blackwitch you should always backup the profile before trying out anything.For the time being do a system restore and you’ll get back the bookmarks and after that use Mozbackup utility to backup your firefox profile before proceeding further.

  8. DesignHamper

    Nice Post I also wrote ‘Become Master in Firefox Profiles on Windows & Make Firefox portable without any tools’

  9. Anil

    Hey thanks man…Everything working perfectly

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