Let's say, Firefox's instance is running with profile 1. Is it now possible, to start a new Firefox instance with profile 2?

Normally, when Firefox is already running, no new instance is created. Instead, just a new browser window is opened.

Note: By saying "profile", I'm referring to Firefox user profiles.

  • try searching. it is the number one question regarding firefox in superuser.com – Capi Etheriel Jan 25 '10 at 15:08

Here's an article from Lifehacker dealing with this. It's not extremely complicated, I've used this a couple of times.

  • Wow! Couldn't imagine that it's so simple and supported out-of-the-box ;) Thanks! – linux_is_for_desktop Sep 15 '09 at 8:14

You can do it from the command line:

firefox -no-remote -P profile_name
  • 2
    First run 'firefox --profilemanager' to set up separate profiles. – postfuturist Oct 30 '09 at 22:23
  • 2
    -P is a shorthand for that – hasen Oct 31 '09 at 23:25
  • 1
    It isn't really: -P says 'load the named profile' it will only open ProfileManager it the profile you've named doesn't exist. – robertc Jan 25 '10 at 14:11
  • firefox -no-remote -P brings up the profile manager for me. Anyway, you can avoid dealing with the Profile Manager at all using the -profile switch as described in my answer. – Nickolay Apr 13 '15 at 21:06

Try MultiFirefox:

MultiFirefox is a small launcher utility that allows you to run multiple versions of Firefox side-by-side. It helps you set up multiple profiles (one or more for each version of Firefox), remembers your last launch preferences for easy launching, has auto-updating built in for when we make improvements, and is 100% open source, MIT licensed.

  • Welcome to SU. Please provide more information then just a link. SU is a repository of answers and desciptive answers are encouraged. – BinaryMisfit Sep 15 '09 at 11:25
  • It is an external tool, which allows multiple instances of firefox to be started, also with different profiles and different sets of addons. – brandstaetter Sep 15 '09 at 11:27
  • Also, it is way more comfortable than using the built-in profile manager. Give it a try, a frined uses it all the time: He launches one instance for web developing with loads of add-ons, and one sleek with minimal add-ons for the usual web surfing, without the add-on bloat. – brandstaetter Sep 15 '09 at 11:37
  • @brandstaetter: I edited your answer a bit to add more info about the app from the authors site. Hope you don't mind! Also, cool little app :) – alex Sep 15 '09 at 12:04
  • awesome, thanks @alex. I'm still getting used to this here, Hope to improve my skills soon :) – brandstaetter Sep 15 '09 at 12:07

Using an unx environement, you can use a command like :

env MOZ_NO_REMOTE=1 firefox -P Profile2

Using a windows or Mac OS X env, I don't know how you can do it

  • OSX is pretty much an unx environment, so it works there as well. – Erika Sep 19 '13 at 14:15

An alternative to using the Profile manager (the -P switch described in @hasen's answer) is to specify the path to profile directly in the command line.

firefox -no-remote -profile absolute-path-to-the-profile-dir will create the directory specified (if it doesn't exist) and use it as the profile.

Example on Windows:

C:\Progra~1\Firefox\firefox.exe -no-remote -profile C:\FxProfiles\myprofile

On OS X it is slightly more complicated:

/Applications/Firefox.app/Contents/MacOS/firefox-bin -foreground \
   -no-remote -profile /Users/me/fx-profiles/myprofile

-foreground switches from the terminal window to Firefox. Note that on 10.5 you have to use an even more complicated comand to work around the dyld error.

See also Starting Firefox with a specified profile from the dock (Mac OS X).

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