Why Microsoft jumped from Windows 8 straight to Windows 10
Microsoft never released a Windows 9. Executives said the new system was too big a leap for that number, and joked that Windows One was taken because Windows 1.0 already existed. Former Microsoft engineer Dave Plummer offered a geekier theory: old programs checking for a name starting Windows 9 might think they were on Windows 95.
The project began as Threshold, named after a planet in the Halo games, and was meant as a wave of systems uniting PCs, phones, tablets and the Xbox on one platform. Announcing it on 30 September 2014, Terry Myerson promised to bring back interface habits from Windows 7 for mouse and keyboard users, who had disliked Windows 8's touch-first design. Another executive, Tony Prophet, said the product was a material step rather than an incremental one, so Windows 9 simply came and went.
The finished system restored the Start menu and added the Cortana assistant, virtual desktops, Windows Hello face and fingerprint login, and the Edge browser, which pushed Internet Explorer aside. It went on general sale on 29 July 2015 as a free upgrade for Windows 7, 8 and 8.1 users. The release build was numbered 10240, a figure the press noticed had a mathematical link to ten, and at launch it shipped in 190 countries and 111 languages.
At a 2015 conference, Microsoft employee Jerry Nixon called it the last version of Windows, reflecting a plan to keep updating one product indefinitely as a service. PC World later argued the line had been taken out of context. Either way, Windows 11 replaced it in October 2021, and mainstream support ended on 14 October 2025.
Adoption lagged the company's ambitions. Microsoft had aimed for a billion devices within three years but only reached that mark in March 2020, almost five years after launch. Reviewers liked the return of the desktop but objected to forced updates, data collection and pushy upgrade prompts.
Source: Windows 10
