/ How To

How to run multiple instances of Firefox simultaneously on macOS

When you try to start two different Firefox versions at the same time (like stable and nightly) you'll get a message that you can only run one instance of it at a time.

Here's how to get around that:

  1. First open the first Firefox version as usual
  2. Now start the second one using the Terminal like this: open /Applications/FirefoxNightly.app --args -ProfileManager (On *nix systems other than macOS it's enough to just run the executable with -ProfileManager)
  3. Create a new profile in the now open window and either start using it right away or open it with -no-remote -P [profilename]

Now you should be running two versions of Firefox simultaneously.

More info on Firefox arguments can be found here and the blog post where I got this from here.



vegan, programmer, musician, critical of everything & worst nightmare of every sysop.

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