Microsoft has served up some important improvements to Windows Sandbox, the space in the next version of Windows 10 for safely running untrusted executable files.

Windows Sandbox is set to debut in Windows 19H1, aka version 1903, which Microsoft is finalizing over the next few weeks for release this spring.

Microsoft introduced Windows Sandbox in the 19H1 preview build 18305 this past December, offering users an ephemeral, containerized desktop environment to run untrusted apps.

Windows Sandbox is available on Windows 10 Pro and Enterprise, and can be enabled from the Windows Features dialog in Control Panel. Users can copy an executable from the host, and then paste and run it in Windows Sandbox without exposing the host to anything nasty.

The latest Fast Ring preview from the 19H1 branch is build 18353 and it delivers a number of new features to Windows Sandbox.

The build enables a device's microphone in Windows Sandbox to improve accessibility capabilities and includes new options to configure the audio input device from a Windows Sandbox configuration file.

There are also new shortcuts for Windows Sandbox, including a shift+alt+PrintScreen sequence that triggers an 'ease of access' dialog for enabling high contrast mode, and a ctrl+alt+break key sequence for going into or leaving fullscreen mode.

It also includes a Windows Sandbox fix for a bug that caused its timezone to be out of sync with the host.

SEE: 20 pro tips to make Windows 10 work the way you want (free PDF)

This build also addresses a number of glitches Windows Insiders have been enduring in recent previews. For some reason, closing a lid or unplugging a monitor would trigger unnecessary bug checks. The past few releases have also nixed users' preferred region settings.

Windows testers who use the Chinese version of games should now find that they work again. Microsoft in February blocked a build to users with PCs set to ZD-CN due to popular Chinese games crashing on launch.

That build was also causing green screen of death (GSOD) errors caused by gaming anti-cheat codes. Microsoft officials blamed the gaming GSOD for the absence of a new Slow Build, but said the error required a fix from third-party developers. According to its release notes, that issue hasn't yet been fixed in this Fast Ring build.

Windows 10 19H1 also appears to be having problems with VMware, a rival to Microsoft's own virtualization tool Hyper-V. VMware can't install or update Windows Insider preview builds for some users. Microsoft says Hyper-V is a "viable alternative".

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