After releasing Windows 10 19H1 build 18351 to Fast Ring Insiders, Microsoft is now rolling out a new build 20H1 to Skip Ahead Insiders. Until now, builds of this new development branch have not brought any new features, and the same can be said for this new build 18850.
The release notes for the new build mention an update for the Snip & Sketch app, which is currently rolling out to Insiders, but this new version is not tied to the installation of build 18850. Snip and Sketch version 10.1901.10521.0 will now use .png as the default save format, and you'll also notice Narrator (screen reader) confirmations when a snip is copied to the clipboard.
Apart from that, this new version brings improvements for Microsoft Edge, Windows Sandbox and more, but Microsoft has yet to fix issues related to anti-cheat software and Creative X-Fi sound cards. Full details about the release are available here.
According to a recent report by Mary Jo Foley of ZDNet, this early testing of 20H1 builds is the result of Microsoft's desire to parallel the release of Azure and Windows. However, the Windows Insider team still plans to release 19H2 builds to Insiders later this spring, once 19H1 is complete.
