Download the installer for the version you want. During the install, switch to Manual, and change the install directory to whatever you want.

I have 3 Firefox installed;

C:\Program Files (x86)\Mozilla Firefox C:\Program Files (x86)\Mozilla Firefox 51 C:\Program Files (x86)\Mozilla Firefox esr

Thanks FredMcD......

Will the new FF version use the same profile as my usual (older) FF version that I use every day, and need for visual impairment addons, or do I need a separate profile ?

Also, will the new version interfere or change any of my FF or Windows configuration settings ?

Thanks... John

Yes, a newly installed Firefox version will use the existing default Profile. You'll need to create a new Profile for the additional newly installed version of Firefox, and make sure that you always use that new Profile. There were a number of changes to the makeup of the Profile in Firefox 55 vs the older versions, which could create issues when "going back" to the older / existing version.

The last installed version of Firefox will have the Windows Registry "rights" for stuff like default browser and such. Doesn't make any difference as to the version number being higher or lower, just being the "last installed" version.

Installing multiple versions on Mac OS X is basically dragging the Firefox application out of the DMG file to the desktop and rename the folder. You can drag the renamed Firefox application folder to the Applications folder like you would normally install Firefox.

You need to use the terminal to create a new profile for that version. Firefox also comes with the about:profiles page that has a button to create a new profile.

Make sure that no profile is selected as Default=1 to make the Profile Manager show when you start Firefox. You can check that in the profiles.ini file.

• http://kb.mozillazine.org/profiles.ini_file
• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles