PC users running the Windows Insider Program are getting a new Windows 10 preview. Microsoft has rolled out two pre-release builds, one for the upcoming Spring Creators Update (Redstone 4) and one for Redstone 5.

This marks something of a rarity from Microsoft. It is not often that two preview builds arrive on the same day. We can probably get used to seeing this practice, however, as Microsoft now develops two Windows branches side-by-side.

Redstone 4, now known as the Spring Creators Update has been in development for months. It will be officially unveiled next month.

However, Microsoft now operates a Skip Ahead feature that allows Insiders to move ahead to the next preview phase. That is Redstone 5, which will launch later in the year.

Windows 10 build 17123

The Redstone 4 (RS4) in this week’s rollout is build 17123. The release adds a couple of new abilities, such as support for the HEIF image container. HEIF uses cutting edge codecs like HEVC to ensure improved quality and compression compared to older formats like PNG and JPEG. At the moment, HEIF support is limited to viewing images, with no editing tools available.

HEIF support is available through the recently launched Windows App Preview Program in the Photos App. For reference, the app should be running version 2018.18022.13740.0 or newer for the HEIF support to work.

Windows 10 build 17123 also added the following bug fixes and improvements:

  • “Fixed an issue from the last flight on PCs with the Dolby Access app installed and expired Dolby Atmos license, where the Windows Audio service (audiosrv) would crash with a stack overflow exception and the PC won’t have sound.
  • Fixed an issue resulting in a bug check with the error message SECURE_KERNEL_ERROR in recent flights.
  • As of Build 17063, a change was made that may have caused some older drivers to not load properly. This may have caused update failures or bugchecks (GSODs) shortly after the PC was rebooted. This build includes fixes for this that should prevent these update failures and bugchecks from occurring.
  • If you clean install, reset your PC, or upgrade straight to this build from the Fall Creators Update the Embedded Handwriting Panel experience will be turned off by default. The setting will remain on for Insiders who have upgraded from previous builds where it was enabled, and can be turned on by anyone with a pen capable device via the “Write directly into text field” option under Pen & Windows Ink Settings.
  • Windows Mixed Reality: The ambient sound in Skyloft should now the correct volume.
  • Windows Mixed Reality: Launching the Store from Movies & TV should no longer crash either app.
  • Windows Mixed Reality: 360 videos should render correctly inside of the Edge app, and the 360 Viewer can be launched from directly from the Store app.”

Windows 10 build 17623

Once Microsoft launched Redstone 4 next month, we expect the Redstone 5 feature development to kick into full gear. At the moment, the Skip Ahead previews for RS5 are limited to a small number of changes.

Through build 17623, Microsoft has included a new safe removal method for GPUs connected by Thunderbolt 3. Windows 10 will now say which apps are using an external GPU so they can be unloaded safely.

Additionally, the latest preview for RS5 now opens links in Windows Mail directly into Microsoft Edge. That company says this “provides the best, most secure and consistent experience on Windows 10 and across your devices.”

Windows 10 build 17623 comes with the following bug fixes and improvements:

  • “Fixed two issues impacting the usability of Windows Mixed Reality on the previous build (Windows Mixed Reality running at a very low frame rate (8-10fps), and a potential crash at startup that could cause Windows Mixed Reality to not work).
  • Fixed an issue resulting in not being able to interact with title bars using touch when Sets was enabled.
  • Fixed an issue resulting in the touch keyboard crashing when focus was moved to certain password fields.
  • We’ve improved the performance of Bluetooth mice when the system is under load.
  • Fixed an issue from recent flights causing precision touchpads to periodically need a few tries to be able to move the mouse.
  • Fixed an issue resulting in the Amharic keyboard not working in Win32 apps.
  • Fixed an issue where EFI and Recovery partitions were unexpectedly listed in Defragment and Optimize Drives.
  • Fixed an issue optimizing drives in Defragment and Optimize Drives didn’t work in the last few flights.
  • Fixed an issue resulting in a permanently black window if you dragged a tab out of a Microsoft Edge window, pulled it up to the top edge of the screen, and moved it back down and released it.
  • Updated the Cortana section in Settings to now be called “Cortana & Search”.
  • Fixed an issue where you couldn’t use touch to interact with the Timeline scrollbar.
  • Fixed an issue where a failed app update could result in that app becoming unpinned from the taskbar.
  • Fixed an issue where if focus was set inside Action Center pressing Esc wouldn’t close the Action Center window.
  • Fixed an issue that could result in ShellExperienceHost periodically waking the device from hibernate if active live tiles were pinned to Start.”