Microsoft today released a new Windows 10 preview with improvements to disk space management, Reset this PC, and the Windows Subsystem for Linux (WSL). The update bumps Windows 10 from build 18309 (made available to testers on January 3) to build 18312. These builds are from the 19H1 branch, which represents the Windows 10 update that will arrive in the first half of this year.

Windows 10 is being developed as a service, meaning it receives new features on a regular basis. Microsoft has released six major updates so far: November Update, Anniversary Update, Creators Update, Fall Creators Update, April 2018 Update, and October 2018 Update.

The seventh update will change how Windows 10 manages disk space. Some disk space (about 7GB) will be set aside as “reserved storage” for updates, apps, temporary files, and system caches. The goal, Microsoft says, is to ensure critical OS functions always have access to disk space. Reserved storage will only be introduced automatically on PCs that come with 19H1 pre-installed or on PCs where 19H1 was clean installed. You can try reserved storage on this build by running this quest.

Next, Microsoft has added new UI for “Reset this PC” (Settings => Update & Security => Recovery). The new UI requires fewer clicks and is more consistent across devices with different configurations.

This build also adds new command line options to the WSL command line tool (wsl.exe). Among the changes (release notes) you can expect consolidated command line options; the option to import a distro for easy sideloading, including to non-system drives; and the option to export your WSL distribution for simpler environment management.

Lastly, this build raises that per-process Fiber Local Storage (FLS) slot allocation ceiling. This is helpful for musicians who hit the FLS limit, which prevented them from loading many plugins into their DAWs (Digital Audio Workstations). The change will also positively impact any application that dynamically loads hundreds or thousands of unique DLLs that have statically linked Visual C++ runtimes.

Bug fixes and known issues

This 19H1 build includes the following general bug fixes and improvements:

Fixed an issue where the Network shares page in File Explorer used black text in dark theme.

Fixed an issue impacting Microsoft Edge reliability in the last few builds.

Fixed an issue where USB printers may appear twice in Devices and Printers under Control Panel.

Fixed an issue where the console would lose color when spawning a new Command Prompt.

Following up on our work earlier this release to make the console scrollbar dark when dark theme is enabled, the title bar will also now bar dark (if you haven’t chosen in Settings to use your accent color in the title bar).

Added a group policy for disabling acrylic on the sign-in screen. This can be found in Group Policy Editor under Administrative Templates > System > Logon > “Show clear logon background”.

Fixed an issue where custom desktop/Lock screen images deployed by a runtime provisioning package would be removed after Windows Update.

Fixed an issue where the shadow behind a flyout might zoom in after the flyout appeared.

Fixed an issue where, if enabled, the Windows Start Up Sound might not play after turning on from shutdown or after updating.

Fixed an issue where the File Properties dialog wouldn’t show the full timestamp if “Conversational format” was selected for the Date Modified column in File Explorer.

Fixed an issue where the hyperlink colors needed to be refined in Dark Mode in Sticky Notes if Insights were enabled.

If you were experiencing Sticky Notes stuck on Loading with Build 18309, check the Microsoft Store for Sticky Notes version 3.5.4.

This build has 16 known issues:

The Windows Security app may show an unknown status for the Virus & threat protection area, or not refresh properly. This may occur after upgrade, restart, or settings changes.

Launching games that use anti-cheat software may trigger a bugcheck (GSOD).

Clicking your account in Cortana Permissions doesn’t bringing up the UI to sign out from Cortana (if you were already signed in) for some users in this build.

Creative X-Fi sound cards are not functioning properly.

When attempting to update this build some S Mode devices will download and restart, but fail the update.

Night light functionality is impacted by a bug in this build.

When you open Action Center the quick actions section may be missing.

Clicking the network button on the sign-in screen doesn’t work.

Some text in the Windows Security app may not currently be correct, or may be missing. This may impact the ability to use some features, such as filtering Protection history.

Windows feature update may fail but show up as a successful update in Windows Update history page. If this happens you will see more than one successful install for the same update in the history page.

Users may see a warning that their USB is currently in use when trying to eject it using File Explorer. To avoid this warning, close down all open File Explorer windows and eject USB media using the system tray by clicking on ‘Safely Remove Hardware and Eject Media’ and then selecting the drive to eject.

When performing Reset this PC and selecting Keep my files on a device that has Reserved Storage enabled the user will need to initiate an extra reboot to ensure Reserved Storage is working again properly.

There is an issue impacting a small number of users enrolled in Microsoft Intune where they may not receive policies. Those policies are not applied and left in “pending“ state on the server. The workaround is to go to Settings/Accounts/Access work or school and “Disconnect” your Azure AD account and then re-enroll.

Windows Sandbox does not load on PCs with multiple GPUs.

In some cases, launching Centennial apps will cause a bindflt.sys bugcheck (GSOD).

If you install any of the recent builds from the Fast ring and switch to the Slow ring – optional content such as enabling developer mode will fail. You will have to remain in the Fast ring to add/install/enable optional content. This is because optional content will only install on builds approved for specific rings.

As always, don’t install this on your production machine.