Starting in Firefox version 43.0, a 64-bit version of the Firefox browser is available. Currently, neither the 32-bit nor 64-bit versions are marked in the Firefox About page with their respective versions. However, there are other ways to determine whether you have the 32-bit or 64-bit version of Firefox installed.

User Agent

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

To access your user agent, you will need to open the Troubleshooting Information page. To do so, click the menu button , click help and select Troubleshooting Information.

In the User Agent section of this page, look at the information enclosed within the parentheses. This contains your operating system number, what bit version your Firefox is, and what Firefox version number you are running.

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. In the brackets, you will find what bit version of Firefox you are using, and your 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.