Microsoft kicked off 2016 with a milestone: Windows 10 is now active on more than 200 million devices, Microsoft VP for Windows Yusuf Mehdi wrote in a blog post Jan. 4.

That’s up from 110 million, the last figure Microsoft reported in October 2015, and the fastest growth in adoption rates of any Windows version so far, according to Mehdi.

It appears Microsoft’s aggressive urging of current Windows users to upgrade has been paying off. Also lending a hand, a Microsoft spokesperson told ZDnet: the recent Xbox One update that brought Windows 10 to those gaming consoles.

While the company is still a long way from its stated goal of one billion devices running Windows 10 by 2018, the new numbers represent strong performance for an operating system that was launched five months ago.

In hardware news, the company announced that Surface Book will be available for pre-order in a number of new markets, including China, Hong Kong, Austria, Australia, the UK, France, Germany, Switzerland and New Zealand by Jan. 5, with Japan to follow shortly. Surface Pro will be available in India “in the coming weeks,” Mehdi wrote.

Mehdi also said demand for the Lumia 950 and 950XL, the first phones to run Windows 10, was outpacing supply in some areas, and that the company was working to restock stores that had run out.

And he touted the doubling of purchases by PC and tablet users in Windows Store over the holiday season—a reminder that for developers, these Windows 10 activation numbers represent more than just bragging rights for Microsoft. The potential market for universal Windows apps is growing, which makes this one a milestone for all of us.