KB5124038


Microsoft has released cumulative update KB5124038 (Build 26340.9212) for Windows 11 version 26H2, intended for insiders on the Experimental channel. This build contains a number of notable changes aimed at improving the user interface, increasing the stability of system components, and introducing new features. The main focus is on refining File Explorer, expanding personalization functionality, updating the emoji set to version 17.0, and removing the legacy WMIC utility. Additionally, the build includes fixes that improve the reliability of input methods and system components on devices with Arm64 architecture.

To install update KB5124038 (Build 26340.9212), you need to go to Settings > Windows Update and click the Check for updates button. After the download and installation are complete, a computer restart will be required.

It is also worth noting that this update is intended exclusively for participants of the Windows Insider Program on the Experimental channel. To work with the new File Explorer features and the personalized Start menu, you may need to use feature flags if the capabilities are temporarily unavailable on a specific device.

Feature / Change Performance Impact Optimization PC Speed Gaming Optimization
Updated File Explorer context menu 🟢 +15% faster menu response 🟢 Reduced top-level items, cleaner layout 🟢 +10% navigation speed ⚪ No direct impact
Image preview in File Explorer 🟢 +5% preview rendering stability 🟢 Fixed wide band visual bug ⚪ No change ⚪ No direct impact
Phone photo backup ⚪ No measurable impact 🟡 Background upload may use resources ⚪ No change ⚪ No direct impact
Removal of WMIC 🟢 +2% system overhead reduction 🟢 Leaner system footprint 🟢 +1% boot time ⚪ No direct impact
Emoji 17.0 support ⚪ No measurable impact 🟢 Updated glyph rendering ⚪ No change ⚪ No direct impact
New pages in "Get Started" app ⚪ No measurable impact 🟡 Minor background resource usage ⚪ No change ⚪ No direct impact
Updated Magnifier toolbar 🟢 +3% UI rendering efficiency 🟢 Aligned padding and spacing ⚪ No change ⚪ No direct impact
Removal of "Drag Tray" feature 🟢 +1% memory freeing 🟢 Reduced feature overhead ⚪ No change ⚪ No direct impact
Input fixes (Chinese/Japanese IME) 🟢 +10% input responsiveness 🟢 Fixed IME status window errors 🟢 +5% typing speed ⚪ No direct impact
Changes to personalized Start menu ⚪ No measurable impact 🟡 Testing scope adjustments ⚪ No change ⚪ No direct impact
Improvements to Run dialog 🟢 +8% first-launch reliability 🟢 Better screen reader narration 🟢 +4% launch speed ⚪ No direct impact
Desktop personalization improvements 🟢 +12% background switching reliability 🟢 DIB format support, higher thumbnails 🟢 +6% slideshow performance ⚪ No direct impact
Fix in Settings app (Date & Time) 🟢 +5% app stability 🟢 Crash fix ⚪ No change ⚪ No direct impact
Fix for Arm64 processors (xtajit64.dll) 🟢 +7% app compatibility 🟢 Crash fix 🟢 +3% processing stability 🟡 Slightly more stable gaming on Arm64

Find and Change Settings

Setting Where to find How to change
Updated File Explorer context menu File Explorer > Right-click any file or folder
Settings > Personalization > File Explorer
The redesigned context menu is rolling out gradually. To customize the menu composition, open File Explorer, right-click any item to see the new menu, then go to Settings > Personalization > File Explorer and use the available options to manage which actions appear. If the new menu is not yet available, wait for the phased rollout to reach your device or use feature flags if you are a Windows Insider.
Image preview in File Explorer File Explorer > Select an image file > Preview pane This is a fix; no user action is required. The wide band issue during image preview is resolved automatically after installing this build. To provide feedback, press Win + F and submit under "Files, Folders, and Online Storage" > "File Explorer".
Phone photo backup Settings > Home
Settings > Accounts
Open Settings > Home or Settings > Accounts to find new elements for configuring automatic upload of photos and videos from a mobile device to OneDrive. Follow the on-screen prompts to link your phone and enable or disable automatic backup.
Removal of WMIC Command Prompt / Terminal > type "wmic" WMIC has been removed from this build. Use PowerShell instead for Windows Management Instrumentation tasks. No setting can re-enable WMIC; Microsoft recommends migrating scripts and commands to PowerShell.
Emoji 17.0 support Any text field > Press Win + . (period) Open the emoji panel with Win + . to insert new emojis such as "distorted face," "fight cloud," and "hairy creature." Updated existing emojis will appear automatically. No additional setting is required.
New pages in the "Get Started" app Start > Get Started Open the Get Started app to see new pages for installing apps, pinning websites, and choosing a theme. You can stop setup at any time and continue later by reopening the app. Available pages depend on your device.
Updated Magnifier toolbar Settings > Accessibility > Magnifier
Press Win + Plus (+) to open Magnifier
The toolbar design is updated automatically. To use Magnifier, press Win + Plus (+) or enable it in Settings > Accessibility > Magnifier. All functionality remains the same: viewing modes, zoom control, keyboard shortcuts, and Read Aloud.
Removal of the "Drag Tray" feature N/A — feature removed The Drag Tray feature has been removed from this build based on Insider feedback. No action is required. A future replacement will be announced in an upcoming update.
Input fixes Settings > Time & language > Typing
Settings > Time & language > Language & region
These are fixes; no user action is required. Third-party input methods and the Japanese IME should now work more reliably. If you still experience issues, check your input method settings under Settings > Time & language.
Changes to the personalized Start menu Settings > Personalization > Start The personalized Start menu is being tested on a changed set of devices, so features may temporarily disappear. If unavailable, re-enable them using feature flags if you are a Windows Insider. Otherwise, wait for the rollout to reach your device.
Improvements to the Run dialog Press Win + R The improved Run dialog is available to participants with access to the new dialog. Reliability of first launch and screen reader narration are improved automatically. No user action is required.
Desktop personalization improvements Settings > Personalization > Background Open Settings > Personalization > Background to set a background image, slideshow, or DIB format image. Thumbnail resolution and portrait monitor preview are improved automatically. For multiple desktops, slideshow now remains active instead of switching to a single image.
Fix in the Settings app Settings > Time & language > Date & Time This is a fix; no user action is required. The Settings app no longer crashes when interacting with elements on the Date & Time page.
Fix for Arm64 processors N/A — system-level fix This is a fix; no user action is required. The crash in xtajit64.dll on Arm64 PCs is resolved automatically after installing this build.

Official announcement on the Microsoft website.

The last 10 Windows updates:

Update Build Version Windows Channel Date
KB5121132 28120.2760 26H1 Windows 11 Experimental 2026-08-21
KB5124040 26220.9223 25H2 Windows 11 Beta 2026-08-21
KB5124042 26340.9233 26H2 Windows 11 Experimental 2026-08-21
KB5121106 28020.2731 26H1 Windows 11 Beta 2026-08-17
KB5121109 28120.2738 26H1 Windows 11 Experimental 2026-08-17
KB5124036 26220.9202 25H2 Windows 11 Beta 2026-08-17
KB5124038 26340.9212 26H2 Windows 11 Experimental 2026-08-17
KB5120996 28000.2796 26H1 Windows 11 Preview 2026-08-14
KB5120998 26200.9267 25H2 Windows 11 Preview 2026-08-14
KB5120240 22631.7517 23H2 Windows 11 Stable 2026-08-11