Most web browsers are installed in Windows as 64-bit versions by default, Firefox being the exception. If you installed the default download of Firefox, you have the 32-bit version, not the 64-bit version, even if you’re running a 64-bit version of Windows.
Say you recently got a new Windows computer. After installing the 32-bit version of Firefox from the main page, you installed your favorite add-ons, restored your backed up bookmarks, and even set up multiple profiles for personal and work purposes. But, now you want to upgrade to the 64-bit version of Firefox for better performance. You could uninstall the 32-bit version and then install the 64-bit version, but doing so will remove your Firefox user data, such as saved passwords, bookmarks, settings, extensions, and themes.
You could back up your profile folders from the 32-bit version of Firefox and then restore them after uninstalling Firefox and installing the 64-bit version. But that’s a bit of a hassle, and there is an easier way.
NOTE: Firefox 64-bit can only be installed on 64-bit Windows. If you’re not sure which version of Windows you’re running, you can easily check. If you’re running 32-bit Windows, you cannot upgrade Firefox to 64-bit.
If you’re not sure if you’re running 32-bit or 64-bit Firefox,…