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


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?

Best Answer

  • 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)

    Task Manager

    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.


    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.

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