Windows Phone 8.1, rolled out at Microsoft's Build Conference in San Francisco, California, on April 2, 2014, is the third and current generation of Microsoft's Windows Phone mobile operating system, succeeding Windows Phone 8.[4] It was released in final form to Windows Phone developers on April 14, 2014, reached general availability on July 15, 2014.[5][6][7][8][9] All Windows Phones running Windows Phone 8 will be upgraded to Windows Phone 8.1,[10] with release dependent on carrier rollout dates.[11]
Windows Phone 8.1 will be succeeded by Windows 10 (mobile). Most Windows Phone 8.1 devices will be capable of being upgraded to Windows 10 (mobile), subject to device compatibility.[12]