Hello,

Normally you can't run different versions of Firefox side-by-side (with the exception of Firefox Developer Edition), so I think when you install the 64-bit version it will uninstall and replace your 32-bit version.

No. Installing Win64 Firefox won't overwrite a 32-bit version. Each '-bit' version installs to a different Program Files sub-folder than the other; 32-bit would be in a (x32) sub-folder. Edit: Sorry - I was wrong about that. Other users have posted that installing 64-bit replaced the 32-bit version. Can't test it myself as my current PC is running a 32-bit version of Win7. The 64-bit I was using in the past is gone back to its' owner. If you want both 64 and 32-bit versions installed you'll need to do a custom installation of the 2nd into its' own PF folder, so you don't overwrite the 1st.

Yes you can have both the 32-bit and 64-bit versions installed together, but you can't run them simultaneously (IOW, side-by-side). They may have separate Program Files folders, but they would share the same Profile folder in AppData. The Profile becomes 'locked' when Firefox is running, so a 2nd process can't access the Profile when the 1st is using it. That limits multiple simultaneous Firefox executable processes from being run and stops the same Profile from being accessed by multiple Firefox processes. (Tells the user that "Firefox is already running".)

But as mentioned about the Developer Edition (doesn't do simultaneous Profiles as implied, but rather allows you to switch Profiles within Firefox DE), an advanced level user who is familiar with Windows command line parameters and is comfortable using them, there is a way to run multiple, simultaneous processes each with it's own Profile, but Mozilla doesn't support it; this forum and KB doesn't provide that information.

If you are curious about running multiple, simultaneous processes, see this thread at a different Firefox support fora. http://forums.mozillazine.org/viewtopic.php?f=23&t=2821799 It was written from a different perspective but the 'drill' is the same.

the-edmeister said

No! Installing Win64 Firefox won't overwrite a 32-bit version. Each '-bit' version installs to a different Program Files sub-folder than the other; 32-bit would be in a (x32) sub-folder.

I just installed the 64 bit version (43.0.1). By default it was installed in C:\Program Files (x86) not in C:\Program Files. It deleted the existing 32 bit version.

JR

Hello,

You can re-install Firefox 32-bit if you want. It should replace the 64-bit version.

Gert Van Waelvelde said

Hello, You can re-install Firefox 32-bit if you want. It should replace the 64-bit version.

The better url is www.mozilla.org/firefox/all as no need to link directly to a version of a specific language to get 32-bit version for Windows.

Joergen said

I just installed the 64 bit version (43.0.1). By default it was installed in C:\Program Files (x86) not in C:\Program Files. It deleted the existing 32 bit version. JR

I tried to install the 64-bit version, and it wanted to install in "c:\Program Files (x86)\". Instead of proceeding, I removed the 32-bit version and tried again. This time, it correctly selected the "c:\Program Files\" folder.

I was actually wanting to run both 32 and 64-bit editions side by side because I was worried that extensions wouldn't work in the 64-bit version. But the only extension that I really want is LastPass, which works.

The 64-bit version has four installed Add-ons. The 32-bit version had eleven. I can't remember all the Add-ons that the 32-bit version had.

Thanks, Shane.