Running two versions of Firefox at the same time

Here’s a tip that will come in handy to those who need to have more than one versions of Firefox running at the same time. I have the current released installed and is my primary browser. I also have the current beta release installed as a portable version (You can get it here).  I keep them both up-to-date and also have their tabs + bookmarks + history + passwords in sync using Firefox Sync.



This can come in very handy because I switch between the two quite often.  See screenshot below.
Two Firefox versions
(Click on the above image to see a larger version)
Until today, I’ve never been able to have both of them running at the same time. Today I discovered a way to tweak the portable version so that it can run along-side the installed instance. Here’s how:
  1. Close any open Firefox windows.
  2. Open your favourite text editor and copy-paste the following text into it:

    [FirefoxPortable]
    AllowMultipleInstances=true
  3. Save the file as “FirefoxPortable.ini” in the folder that you have the portable version installed in. Tip: This is the same folder that contains FirefoxPortable.exe.
Now start each version and watch them run side by side ;-)