I have been looking forward to Windows 10 ever since September 30, 2014, the day it was announced. I reserved the free upgrade from Windows 8.1 on June 1, 2015, the day Microsoft started taking reservations for the free upgrade for practically every computer running non-enterprise versions of Windows 7 and Windows 8.1. I had no doubt Firefox 39 would work without issue on Windows 10 since it was and is poised to combine everything Microsoft received critical acclaim for in both operating systems, and I am curious to know how Firefox 40 will be different from Firefox 39 in Windows 10, due August 11, 2015. I have seen numerous news articles that Firefox 40 is going to be optimized for Windows 10 in that it is the first version of Firefox released after Windows 10's finalization on July 15, 2015, which is Windows NT 10.0.10240. The only difference I've noticed between Firefox 39 on Windows 8.1 and Firefox 39 on Windows 10 is that the bar at the top of the window looks different, probably because of the updated interface in Windows 10. It is noticeably different from any previous version of Windows, and ushers in a new beginning for the coming years of devices running Windows as we know it. It's safe to assume Firefox 40 on Windows 10 will bring about updates to the interface on Firefox's half of the equation, but if there are any kind of performance improvements, then August 11 can't come soon enough.