It's taken nearly a decade but Mozilla has finally released 64-bit version of Firefox for Windows to its stable channel.
Mozilla points out that Firefox 64-bit for Windows offers gains in performance for those running 64-bit systems although it also has limited support for plugins by design. As such, users will notice that some sites requiring plugins that work with 32-bit versions of Firefox may not work with the new 64-bit variant.
As Mozilla has previously stated, it's phasing out support for most NPAPI plugins in Firefox - something it hopes to complete by the end of 2016.
Mozilla has toyed with the idea of a 64-bit version of Firefox for several years, many of which made it to alpha / beta status. In 2012, however, Mozilla elected to halt 64-bit builds entirely due to negative feedback and a frustrating testing experience. Fortunately, the foundation backtracked (albeit quietly) a few months later and resumed development.
As Ars Technica points out, Mozilla promised last year that a 64-bit Windows version would reach the stable channel by the end of 2015. Some thought that was going to happen with the release of Firefox 41 back in September but that intelligence proved inaccurate.
Mozilla did keep its promise in Firefox 43, even if it was with just a couple of weeks to spare. You can pick up the 64-bit version here.