How do I tell if I have the 32-bit or 64-bit Firefox?

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This article applies to Windows and Linux. All Firefox versions are 64-bit on macOS.

Both 32-bit and 64-bit versions of Firefox can be installed on 64-bit Windows and Linux operating systems. See this blog post to learn more.

Not sure whether you're running 32-bit or 64-bit Firefox? This article explains how to find out.

About Firefox window

You can find what version of Firefox you are using in the About Firefox window. Click the menu button Fx89menuButton, click Help and select About Firefox.Click the menu button Fx57Menu, click Fx57Help Help and select About Firefox. The About Mozilla Firefox window will open. (32-bit) or (64-bit) will be shown under the Firefox name, after the version number.

Here is an example of what the About Firefox window will look like:

Note: Opening the About Firefox window will, by default, start an update check. If an updated version of Firefox is available, it will be automatically downloaded. For more information, see Update Firefox to the latest release.

Windows program listing

You can also check the installed version of Firefox from the Windows list of installed programs. Open the Windows Control Panel, click on Programs, then Programs and Features.Open Windows Settings, click on System, then Apps & features. This will show you a list of software that is currently installed on your computer.

To see if the 32-bit or 64-bit version of Firefox is installed, locate Mozilla Firefox in the list of programs. The program name will include the Firefox version and, in parentheses, the bit version and language. If the program name contains x86, the 32-bit version of Firefox is installed. If the program name contains x64, the 64-bit version of Firefox is installed.

Note: You can have both 32-bit and 64-bit Firefox program versions listed, if you installed one version without uninstalling the other. Starting in Firefox version 67, Firefox creates dedicated profiles for each installation (see Recover user data missing after Firefox update if this results in lost data). You can uninstall the unwanted version. The Firefox uninstaller doesn't remove any of your Firefox user profile data, such as passwords or bookmarks.