Today, with the release of Firefox 43, almost a decade after the idea was first mooted, there is finally an official 64-bit build of Firefox for Windows. To download it, you'll have to head over to the Firefox website and explicitly grab a 64-bit installer; if you just do an in-place upgrade you'll just get the normal 32-bit flavour. 64-bit Firefox for Windows is mostly identical to 32-bit Firefox
![Firefox for Windows finally has an official, stable 64-bit build](https://cdn-ak-scissors.b.st-hatena.com/image/square/c77293b9d3657a5e1442047b3c40f0737900d053/height=288;version=1;width=512/https%3A%2F%2Fcdn.arstechnica.net%2Fwp-content%2Fuploads%2F2015%2F12%2Ffirefox-download-64-bit-640x215.jpg)