The first 64 bit release of Firefox for Windows [1] was Firefox 43.0 which was released at the end of 2015 [2] [1] https://www.computerworld.com/article/301538

The first 64 bit release of Firefox for Windows [1] was Firefox 43.0 which was released at the end of 2015 [2] [1] https://www.computerworld.com/article/3015388/mozilla-finally-ships-64-bit-firefox-for-windows.html https://www.computerworld.com/article/3015388/mozilla-finall... [2] https://www.mozilla.org/en-US/firefox/43.0/releasenotes/ https://www.mozilla.org/en-US/firefox/43.0/releasenotes/