You can do it by using software like Sandboxie or a virtual machine.

You could install a virtualized Firefox version and have a different version running in your physical OS.

Well ;) The info from the 3 year old post is still valid. Following trails begun there I...

1. Opened Firefox 1 with the -profilemanager command line switch

2. I renamed the current profile to "Plex".

3. I created a new profile named "Regular".

4. I started Firefox 1 with the new profile "Regular".

5. I closed firefox 1 and manually copied everything from the "Plex" profile folder into the "Regular" profile folder. (Replacing/Overwriting everything)

6. I downloaded "Firefox Setup 55.0.exe" and manually extracted the "Core" folder with Winrar.

(Go here https://www.mozilla.org/en-US/firefox/new/ and click on the "Firefox for other platforms & Languages" to get the full offline installer package)

7. I created a new folder in "program files" (not program files (x86)) and named it Mozilla Firefox.

8. I moved everything from the "Core" folder I extracted from the archive into the new "mozilla Firefox" folder.

9. I created a custom shortcut "C:\Program Files (x86)\Mozilla Firefox\Firefox.exe" -P Plex -no-remote and named it plex and changed the icon to the one from the plex executable. (Firefox 1)

10. I created another shortcut "C:\Program Files\Mozilla Firefox\Firefox.exe" -P Regular (Firefox 2)

11. I started Firefox 2 with the second shortcut from #10 and set it to the default browser.

12. I then stated the 2nd instance of Firefox (Firefox 1) with the shortcut from #9 and told it not to be the default browser and not to check this setting on start up.

Now I have Firefox 32bit v54.0.1 (set to never update) for running my media front end and Firefox 64bit v55 (That I will keep updates current on) for accessing the internet and can run both at the same time.

Good info, even though I'd rather use virtualization.

Should something go south, I revert to a previous snapshot.

I've got the feeling it won't be too long before I give up on Firefox completely.

In the last year or two Mozilla has repeatedly shown total disregard for what the end users actually want and just made whatever changes they they felt were best for us.

This is the reason I quit using other browsers and migrated to Firefox in the first place. I want my programs on my computer to look and function the way I want them too. Not how someone else thinks they should.

I do appreciate all the hard work they put into Firefox but I'm not at all happy with the slowly eroding ability to customize it.

Yes, it’s still possible as outlined in the other question. Some people even run 3 or more instances/versions simultaneously, e.g. developers.

Just make sure to use the -no-remote switch (command line argument) for your second instance at least, or for both if you are not sure which one you’ll start first (or the one without it will just launch as another instance of the one launched with -no-remote if that was the first).

Also make sure to use separate profiles, of course. You might want to fix their names in the same / shortcut to be safe, because a) they can’t use one profile simultaneously, b) you may want to keep them separate at all times anyway, c) you don’t need the Profile Manager (choices dialog) to appear at every launch and d) due to an incompatibility between 54.x and 55+ profiles, a 54 profile will be migrated when used by 55 or higher (most important), possibly by mistake.

E.g. you could change/edit the startup shortcut for the 32-bit Firefox v54.0.1 version as follows:

"C:\Program Files (x86)\Mozilla Firefox\firefox.exe" -p default (if default is the profile name)

...and the one for 64-bit Firefox v55 like this:

"C:\Program Files\Mozilla Firefox\firefox.exe" -no-remote -p 55plus (if "55plus" is the profile name).

The 32-bit shortcut can/should also use -no-remote if you might want to launch it later than the 64-bit version. Make sure to use the proper order for the arguments - I think putting -no-remote at the end will cause it to be ignored.

Also make sure to create a profile before starting the newly installed Firefox 55, using the Profile Manager as described here (or by simply adding -p to the shortcut at first launch), at least for 55, as it will use the default/existing profile by default after installing it and cause the existing profile to be migrated, unless 54 is already running so an error message will follow.

If you would rather update 54 to 55 first and this is about 32-bit and 64-bit only, there is no issue with migrated profiles. However if you haven’t installed 55 yet, I’d suggest to wait until 55.0.1 is released.

I would like to install a second version of Firefox on Linux (Mint) without losing the first one. Has anyone done this?

http://forums.mozillazine.org/viewtopic.php?f=7&t=2400491

http://libre-software.net/how-to-install-firefox-on-ubuntu-linux-mint/

http://odyniec.net/blog/2010/02/running-multiple-versions-of-firefox-in-ubuntu-9-10/

http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Basically you need to get the firefox direct from them with the tar.bz2 file ending, not a .deb file from repository.

Use Archive Manger to open it.

Extract into a new folder you create like "firefox57" under your /home/"user name", maybe best to put into the hidden folder called .mozilla

You then manually create a launcher on desktop and use the firefox command with the -P -no-remote switch in the launcher. Or you could just go to the folder you created "firefox57" first and run it, see if it opens.

The above links give differing approaches, but all are basically the same thing other than where you extract the files.

Once it's working for you, go here to discover how to use CSS to make changes to fit the way you want it to look, since Classic Theme Restorer add-on will not work in it like earlier versions.

https://github.com/Aris-t2/CustomCSSforFx/releases

Theres a few threads on Firefox Quantum at forums.linuxmint.com which might also help you. I am Spearmint2 there.

Can someone explain the below part of the solution. It is looking like I will have to run a few versions earlier of the 32-bit browser after upgrading and switching to the 64-bit browser. Seems like Mozilla and developers have somewhat abandoned the browser with the very limited plug-ins.

"6. I downloaded "Firefox Setup 55.0.exe" and manually extracted the "Core" folder with Winrar."

Can you be specific on what is "Core"?

Thanks.

MadeUpName30 said

1. Opened Firefox 1 with the -profilemanager command line switch 2. I renamed the current profile to "Plex". 3. I created a new profile named "Regular". 4. I started Firefox 1 with the new profile "Regular". 5. I closed firefox 1 and manually copied everything from the "Plex" profile folder into the "Regular" profile folder. (Replacing/Overwriting everything)

• I want to try this but I'm not sure - why did you migrate the profile? Is it essential, or did you just want to keep some stuff in the FFv55 one ?

• Which version opens when you just use (command-line > firefox.exe) ?

tresp said

MadeUpName30 said

1. Opened Firefox 1 with the -profilemanager command line switch 2. I renamed the current profile to "Plex". 3. I created a new profile named "Regular". 4. I started Firefox 1 with the new profile "Regular". 5. I closed firefox 1 and manually copied everything from the "Plex" profile folder into the "Regular" profile folder. (Replacing/Overwriting everything)

• I want to try this but I'm not sure - why did you migrate the profile? Is it essential, or did you just want to keep some stuff in the FFv55 one ?

• Which version opens when you just use (command-line > firefox.exe) ?

He wanted to keep using the existing Profile.

Using only firefox.exe is "fraught with peril". It will open the Default Profile and should the "Default" accidentally get changed by the user problems can arise if / when the Profile is opened in the wrong version of Firefox.

And that can only be done with the "Main" version (the most recently installed version). The "other" version will also use the "Default" Profile, which will cause problems with incompatible addons or can result lost data.

Going thru the Profile Manager all the time isn't a good solution; one "mind-fart" like selecting the wrong Profile for the version of Firefox you are opening and you could have problems.

Bottom line is - you are better off using separate desktop shortcuts to launch each version of Firefox that is installed, with their respective Profile in the command line.

And if that is beyond your skills or you don't want to spend the time to do that, just use the Portable edition of Firefox - which installs completely separate from the official version, so no messing around with "Profiles". https://portableapps.com/apps/internet/firefox_portable https://portableapps.com/apps/internet/firefox-portable-esr

How would extensions and their prefs transfer more reliably - by copying the profile folder or over FEBE ?