Microsoft is now releasing build 12400 of the Windows Phone 8.1 OS preview

Microsoft has thrown the switch on a new release of the Preview for Developers and Windows Phone 8.1. Starting at 1 PM ET, those who are enrolled in the free Preview for Developers program are receiving build 12400 of the OS, which is a small jump from the previous 12397.

Currently, it is not known what changes are brought with the latest release, though it is most likely fixes for stability and other optimizations.

The update is 21 MB in size.

We are updating this article as more information comes in.

Daniel Rubino

Daniel Rubino is the Editor-in-chief of Windows Central. He is also the head reviewer, podcast co-host, and analyst. He has been covering Microsoft since 2007, when this site was called WMExperts (and later Windows Phone Central). His interests include Windows, laptops, next-gen computing, and watches. He has been reviewing laptops since 2015 and is particularly fond of 2-in-1 convertibles, ARM processors, new form factors, and thin-and-light PCs. Before all this tech stuff, he worked on a Ph.D. in linguistics, watched people sleep (for medical purposes!), and ran the projectors at movie theaters because it was fun.