Windows – Where to see which Firefox version is running? (64-bit or 32-bit)

64-bitfirefoxwindows

I downloaded Firefox version 43.0.4, 64-bit from their official site and installed it. Before this, I had the Firefox 32-bit version. My OS is Windows 10, 64-bit.

I did not remove the 32-bit old version, just installed a fresh new 64-bit. When I run the browser, I don't see information anywhere confirming that I'm running the 64-bit version.

Can you tell me where I can find information about the bit version of the browser that is being run?

• In Firefox, type about:support in the the URL window. If you have the menu display turned on, this is also accessible under Help | Troubleshooting Information. The Application Basics section at the top will show you the version you're running.

User Agent

Now that the 64-bit version has been officially released, it carries the same version number as the 32-bit version. So if the version numbers on your computer are the same, you can determine 32-bit vs. 64-bit from the User Agent entry in that section:

• 32-bit Firefox running on 64-bit Windows (8.1, can't verify 10), shows WOW64 in the User Agent.
• 64-bit Firefox running on 64-bit Windows (8.1, can't verify 10), shows Win64; x64.
• 32-bit Firefox running on 32-bit Windows will not include the Win64; x64 in the user agent.

Control Panel

Another place you can differentiate them is the Control Panel | Programs and Features | Uninstall a program. The software name is listed (the version number, 43.0 in this example, may be different):

• 32-bit Firefox is listed as Mozilla Firefox 43.0 (x86 en-US).
• 64-bit Firefox is listed as Mozilla Firefox 43.0 (x64 en-US).

If you have something other than the US English version, the letters after the x86 or x64 will be different. (Source: How to tell if Firefox is 32-bit or 64-bit)

One other place to check, according to Caspid on the Mozilla Support forum, is the Task Manager.

• Start the Task Manager (Ctrl+Shift+Esc).
• 32-bit Firefox will display as firefox.exe *32.

user559862 reported (in a now deleted post), that 64 bit Firefox is displayed as simply firefox.exe in the Task Manager.

Update:

Build Platform Target

It looks like there's yet another place to identify this, which you found, and I'll add it here for completeness. If you enter the URL about:buildconfig (which also has a link in the Application Basics section), it has a section called Build Platform Target. This includes a similar identification indicator. A 64-bit Firefox will include the identifier x86_64.