A 64-bit version of Firefox is available for Windows 64-bit operating systems, in addition to the 32-bit version of Firefox (see this blog post for details). This article explains how to determine whether you are running the 32-bit or 64-bit version of Firefox.

User agent

The user agent identifies your browser to websites and contains information about your operating system and browser version. This can be an easy way to identify what version of Firefox you are running.

To find your user agent, click the Firefox menu button , click help and select Troubleshooting Information. This will open the Troubleshooting Information page.

In the Application Basics section of this page, find the User Agent entry and look at the information enclosed within the parentheses. If your user agent contains WOW64, you are running the 32-bit version of Firefox. If your user agent contains Win64; x64, you are running the 64-bit version of Firefox.

Windows program listing

You can also check which version of Firefox you are running from the Programs and Features listing in Windows.

To open the Programs and Features manager, first open your Control Panel in Windows. Then select the Programs category, or Programs and Features if you are using icons. This will load a list of software that is currently installed on your system.

To determine whether your Firefox is 32-bit or 64-bit, locate the Mozilla Firefox program. The program name will include the Firefox version and, in parentheses, the bit version and language.

If your program name contains x86, you are running the 32-bit version of Firefox. If your program name contains x64, you are running the 64-bit version of Firefox.