Announcing Windows Server vNext Preview Build 29531

Hello Windows Server Insiders!

Today we are pleased to release a new build of the next Windows Server Long-Term Servicing Channel (LTSC) Preview that contains both the Desktop Experience and Server Core installation options for Datacenter and Standard editions and Azure Edition (for VM evaluation only). Branding remains Windows Server 2025 in this preview - when reporting issues please refer to Windows Server vNext preview.

Build 29531 establishes a new Server preview baseline build. Please perform a clean install of Build 29531 (or later) using the installation media linked below.

Please note: Upgrades from earlier Windows Server vNext preview builds are not supported. We encourage all Windows Server vNext preview users to perform a clean install to reliably continue in the Windows Server vNext preview program.

While upgrades from earlier Windows Server previews (Build 26525 and older) are not technically blocked by setup.exe, a number of known issues have been identified related to upgrades necessitating a release of a new baseline build for our Server vNext Preview Program.
The new baseline build (29531) will not be Flighted due to upgrade issues. Flighting support will resume with future vNext preview releases.

What's New

[NEW] ReFS Boot is enabled for Windows Server vNext preview builds.

Known Limitations

- ReFS Boot systems create a minimum 2GB WinRE partition.
- When WinRE cannot be updated due to space constraints, the system may disable WinRE. Disabling WinRE does not remove the partition.
- If the WinRE partition is deleted and the boot volume is extended over it, this operation is unrecoverable without a clean install.

For more information, please visit: Resilient File System (ReFS) overview | Microsoft Learn

Feedback Hub app is available for Server Desktop users! The app should automatically update with the latest version, but if it does not, simply Check for updates in the app’s settings tab.

Known Issues

Upgrading from earlier builds of Windows Server vNext previews (26525 or older) are not supported. Please perform a clean install of build 29531 or later.

Users may experience failures when attempting to upgrade from earlier previews (build 26525 and older). VMs may fail to upgrade or start after upgrade from older preview builds impacting live migration and failover cluster scenarios.

Download Windows Server Insider Preview (microsoft.com)

Flighting: The label for this flight may incorrectly reference Windows 11. However, when selected, the package installed is the Windows Server update. Please ignore the label and proceed with installing your flight. This issue will be addressed in a future release.

Available Downloads

Downloads to certain countries may not be available. See Microsoft suspends new sales in Russia - Microsoft On the Issues.

Windows Server Long-Term Servicing Channel Preview in ISO format in 18 languages, and in VHDX format in English only. 
Windows Server Datacenter Azure Edition Preview in ISO and VHDX format, English only.
Microsoft Server Languages and Optional Features Preview

 Keys: Keys are valid for preview builds only 

Server Standard: MFY9F-XBN2F-TYFMP-CCV49-RMYVH
Datacenter: 2KNJJ-33Y9H-2GXGX-KMQWH-G6H67
Azure Edition does not accept a key.

Symbols:  Available on the public symbol server – see Using the Microsoft Symbol Server. 

Expiration: This Windows Server Preview will expire September 15, 2026.

How to Download

Registered Insiders may navigate directly to the Windows Server Insider Preview download page. If you have not yet registered as an Insider, see GETTING STARTED WITH SERVER on the Windows Insiders for Business portal.

We value your feedback!

The most important part of the release cycle is to hear what's working and what needs to be improved, so your feedback is extremely valued. Please use the new Feedback Hub app for Windows Server if you are running a Desktop version of Server. If you are using a Core edition, or if you are unable to use the Feedback Hub app, you can use your registered Windows 10 or Windows 11 Insider device and use the Feedback Hub application.  In the app, choose the Windows Server category and then the appropriate subcategory for your feedback. In the title of the Feedback, please indicate the build number you are providing feedback on as shown below to ensure that your issue is attributed to the right version:

     [Server #####] Title of my feedback

See Give Feedback on Windows Server via Feedback Hub for specifics.

The Windows Server Insiders space on the Microsoft Tech Communities supports preview builds of the next version of Windows Server. Use the forum to collaborate, share and learn from experts.  For versions that have been released to general availability in market, try the Windows Server for IT Pro forum or contact Support for Business.

Diagnostic and Usage Information

Microsoft collects this information over the internet to help keep Windows secure and up to date, troubleshoot problems, and make product improvements. Microsoft server operating systems can be configured to turn diagnostic data off, send Required diagnostic data, or send Optional diagnostic data. During previews, Microsoft asks that you change the default setting to Optional to provide the best automatic feedback and help us improve the final product.

Administrators can change the level of information collection through Settings. For details, see http://aka.ms/winserverdata. Also see the Microsoft Privacy Statement.

Terms of Use

This is pre-release software - it is provided for use "as-is" and is not supported in production environments. Users are responsible for installing any updates that may be made available from Windows Update. All pre-release software made available to you via the Windows Server Insider program is governed by the Insider Terms of Use.