I have a new version of Firefox (46).

I need to install Firefox 44 to find a bug, that appears in a web app I am writing, but only in version 44 and older.

How do I do that? I don't want to have any conflicts, I don't want the older version to overwrite the current settings, etc.

  • 3
    Safest bet would be a virtual machine.
    – Jos
    May 11, 2016 at 11:03
  • Is your problem solved ?
    – ankit7540
    May 12, 2016 at 15:43

2 Answers 2


You have three options.

  1. Use a portable version of firefox.

You can check the link for details: Using portable firefox and fixing flash

  1. Use Virtual machine and use firefox therein.
  2. Install two versions of firefox. (Probably this is what you are looking for.)

Download the older version of firefox from the archive: Mozilla.org_ftp_site

Unzip to a path.

Next open terminal and use the following command to add a new firefox user.

firefox --no-remote -P

Create a new user, take note of the user-name.

Next, create a launcher for the 'firefox' you just unzip. Go inside the unzipped folder , there you will find a firefox file (probably binary) which launches the program. When creating the launcher, update the command as:

/path/to/unzipped/firefox --no-remote -P "<user-name>"

Creating launcher in Ubuntu

And now, when you will use this launcher then older firefox (which you want to use for testing) will open. Important - check the build version to verify.

In the url bar -> about:

(Your newer version of firefox will not be affected, and it has firefox --no-remote -P "default" as command.)

  • 1
    Like you write it now, you will start the same Firefox (you'll need a path to the new Firefox!). Make sure you actually start the right version… Also, it's probably better to use --no-remote (double dash) as documented in firefox --help (the manpage is clearly outdated).
    – JanC
    May 11, 2016 at 12:08
  • 1
    And: a third option is to use a VM, of course.
    – JanC
    May 11, 2016 at 12:10
  • I think the problem is that the .Mozilla directory is shared. I created a standalone unzip gz downloaded file. It is not really "portable". What I need to do is have its own Mozilla directory (not the one in the home directory) Jan 1, 2018 at 9:37

You should create a new Firefox user profile
and install by the -no-remote command line
Please visit: https://support.mozilla.org/en-US/questions/974208

  • I did creat a new profile. It prompted me for it. I called the profile firefox54 Jan 1, 2018 at 9:37

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