​Microsoft has released the KB5079391 preview cumulative update for Windows 11 24H2 and 25H2, which includes 29 changes, such as Smart App Control and Display improvements.

The KB5079391 update is part of Microsoft's non-security preview schedule, which pushes updates at the end of each month to test new features and fixes that will roll out during the next month's Patch Tuesday. However, unlike regular Patch Tuesday cumulative updates, monthly preview updates do not include security updates and are optional.

With the March 2026 optional update, Microsoft is gradually rolling out improvements to the Windows 11 Smart App Control security feature, allowing customers to toggle it without reinstalling the operating system.

"You can turn Smart App Control (SAC) on or off without needing a clean install. To make changes, go to Settings > Windows Security > App & Browser Control > Smart App Control settings. When turned on, SAC helps block untrusted or potentially harmful apps," Microsoft said.

KB5079391 also includes a set of Display reliability improvements, such as support for monitors reporting refresh rates higher than 1000 Hz, native USB4 monitor connections, and improved HDR reliability.

You can install this update either by downloading it from the Microsoft Update Catalog or by opening Settings, clicking Windows Update, and then selecting "Check for Updates."

Because this is an optional update, you will be asked whether you want to install it by clicking the "Download and install" link unless you have the "Get the latest updates as soon as they're they're available" option enabled, which will cause the update to install automatically.

Windows 11 KB5079391 highlights

Once installed, this optional non-security update will upgrade Windows 11 25H2 and 24H2 devices to builds 26200.8116 and 26100.8116, respectively.

The March 2026 preview update adds further improvements, some of the more important ones highlighted below:

• [Performance & Reliability] This update improves stability in Windows Recovery Environment (Windows RE) when you run x64 apps on ARM64 devices. These apps run more smoothly and respond as expected.
• This update improves the reliability of downloading required updates when you're prompted in Settings > System > Advanced.
• [Windows Hello] This update improves the reliability of Windows Hello Fingerprint on certain devices.
• This update improves the design of the dialog boxes in Settings > Accounts > Other users to match the modern Windows look and support dark mode. The visibility of the dialog box option depends on whether the device has a domain-joined work or school account.

Microsoft says there are currently no known issues with this update, and the full release notes are available in this support bulletin.

Last month, the KB5077241 optional cumulative update rolled out improvements to the BitLocker Windows security, native System Monitor (Sysmon) functionality, and a new network speed test tool.