Firefox Gets a 64-bit Version for Windows
In a move that I found to be quite surprising, Mozilla has released a 64-bit version of the Firefox web browser for Windows, a move that is surprising because I just assumed that it had already happened. Mac and Linux users have had a 64-bit version for a while, but it took until release 43 for it to come to Windows. The 64-bit build is for Windows 7 and up, and users of a current 32-bit version will have to download an all new copy rather than upgrading their current install. Users likely won't see much of a difference as "most of the big improvements happen behind the scenes, although the 64-bit version should be able to keep more tabs open without slowing as well as run web apps that require 64-bit support."
Source: PC World