Microsoft has been consistently adding 100 million active Windows 10 devices every six months over the past two years. Windows 10 also passed 50 percent desktop market share in August.

The milestone is notable because Microsoft originally aimed to hit a billion devices running Windows 10 “in two to three years”.

A year in, the company backpedalled on that goal after it became clear that Windows 10 Mobile was a failure. (Android has over 2.5 billion monthly active devices.)

Windows 10 was released four years and eight months ago in July 2015. It thus took the company more than double its ambitious estimate and 20 months longer than its conservative estimate to pass one billion Windows 10 devices.

In October, Vole announced Windows 10X, which is Windows 10 for dual-screen PCs. At the same time, the company unveiled the dual-screen Surface Neo running Windows 10X, while promising dual-screen PCs from partners Asus, Dell, HP, and Lenovo.

Microsoft is also developing Surface Duo, a foldable Android phone. Its mobile OS bet failed, so now Microsoft is double dipping on dual-screen devices. Microsoft’s market position makes it one of the players to watch as the industry attempts to figure out the next form factor.

Microsoft said Windows 10 powers 80,000 models and configurations of laptops and 2-in-1s from over 1,000 different manufacturers. Xbox consoles, and the upcoming Xbox Series X all run Windows 10 variants.