Table of contents
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Release Date:

18/05/2021

Version:

Windows 10, version 21H1

Updates for Windows 10, version 21H1

Windows 10 is a service, which means it gets better through periodic software updates.

The great news is you usually don’t have to do anything! If you have enabled automatic updates, new updates will automatically download and install whenever they’re available, so you don’t have to think about it.

On the left side of this page, you’ll find a list of all the updates released for this version of Windows. You can also find more information about releases and any known issues. Installing the most recent update ensures that you also get any previous updates you might have missed, including any important security fixes.

For more information about the update and how to get it, see: 

What's new for Windows 10, version 21H1, Windows 10, version 20H2, and Windows 10, version 2004 release notes

Windows 10, versions 21H1, 20H2, and 2004 share a common core operating system and an identical set of system files. As a result, the release notes for Windows 10, versions 21H1, 20H2, and 2004 will share an update history page. Each release page will contain a list of addressed issues for 21H1, 20H2, and 2004 versions. Note that the 21H1 and 20H2 versions will always contain the fixes for 2004; however, 2004 will not contain the fixes for 21H1 and 20H2. The update history page will provide you with the build numbers for 21H1, 20H2, and 2004 versions so that it will be easier for support to assist you if you encounter issues.

Current status of Windows 10, version 21H1

For the most up-to-date information about known issues for Windows and Windows Server, please go to the Windows release health dashboard.

Known issues

Symptom

Workaround

Certain Japanese half-width Katakana and full-width Katakana characters that have a consonant mark aren’t interpreted as the same character. When you use the CompareStringEx() function with the NORM_IGNOREWIDTH flag to compare them, these characters are evaluated as different because of an issue in the sorting rule. This issue affects all the updates starting on June 9, 2020 for Windows 10, version 2004.

12/9/20:

  1. Open the Command Prompt window (cmd.exe) with elevated privileges.

  2. Run “reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Nls\Sorting\Versions /ve /d 0006020F /f”

  3. Restart the computer or processes to see the full effect.

Important If you have not installed KB4586853or later on the computer, setting an invalid value in this registry might prevent the computer from starting up.

This workaround reverts the National Language Support (NLS) sorting rule to version 6.2, which is used in Windows 10, version 1909 and earlier. When sharing data between systems, consider applying the workaround consistently. If you use this workaround, conduct sufficient testing and evaluations to mitigate problems caused by different sorting rule versions on multiple systems.

When using the Microsoft Japanese Input Method Editor (IME), applications might not be able to automatically change Roman/Kana input modes.

Note for developers Affected apps are using the ImmSetConversionStatus function or VK_KANA key emulation.

To mitigate this issue, do one of the following:

We are working on a resolution and will provide an update in an upcoming release.

Notes and messages

None.

Troubleshooting

If you have questions or need help activating or troubleshooting Windows, see our help topics below:

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