KB5102951


Microsoft has released cumulative update KB5102951 (build 28120.2387) for Windows 11 Insider Program participants on the Experimental channel. This build belongs to version 26H1 and contains a number of significant changes aimed at increasing interface customization flexibility, as well as special features for the education sector. The main focus of the build is on modernizing the taskbar, which now supports changing its screen position and a new compact display mode for devices with small displays. Additionally, insiders received fixes for issues related to File Explorer and the Outlook app.

As part of fixing known issues, Microsoft resolved an error that caused the OneDrive shortcut in File Explorer to stop functioning when launching the file manager with administrator privileges. Also fixed is an issue with the Outlook app, which last week might not have responded to pressing the close button. No other major documented issues have been identified in this build.

To install update KB5102951, you need to go to SettingsWindows Update and click the Check for updates button. The build will be downloaded and installed automatically; a computer restart is required to complete the process.

It should be remembered that this build is intended exclusively for Windows Insider Program participants on the Experimental channel of version 26H1 and contains changes that are still in the stage of active refinement, including incomplete support for touch gestures for alternative taskbar positions.

Feature / Change Performance Increase or Decrease Optimization PC Speed Gaming Optimization
Taskbar position change 🟡 Neutral to slight decrease (extra rendering for new layouts) 🟢 UI flexibility optimized; animations correctly align to new edges 🟡 Minimal overhead during position switching, otherwise negligible ⚪ No direct impact; touch/auto-hide refinements pending
Smaller taskbar 🟢 Slight increase (reduced GPU/compositing load for smaller elements) 🟢 Screen real estate reclaim optimized; icon and height scaling streamlined 🟡 Marginal gain on compact/low-resolution devices ⚪ Not applicable
Free upgrade to Windows 11 Pro for Education (K-12) ⚪ No impact (licensing change only) 🟢 Deployment workflow optimized for institutional IT ⚪ No measurable change ⚪ Not applicable
OneDrive shortcut fix (admin-privilege File Explorer) 🟢 Slight increase (eliminates hung/blocked UI thread) 🟢 Shell extension reliability optimized 🟡 Faster file-manager response in elevated sessions ⚪ No direct impact
Outlook close-button unresponsiveness fix 🟢 Slight increase (prevents resource leak from unclosed window) 🟢 UI message-loop responsiveness optimized 🟡 Minor improvement when Outlook runs alongside other apps ⚪ No direct impact

Find and Change Settings

Setting Where to find How to change
Taskbar Position Settings → Personalization → Taskbar → Taskbar behaviors Open Settings, go to Personalization, then Taskbar, and expand Taskbar behaviors. Use the dropdown menu to choose the taskbar location on screen: Bottom, Top, Left, or Right. Tooltips, menus, and animations will adjust to the selected side automatically.
Smaller Taskbar Settings → Personalization → Taskbar → Taskbar behaviors Go to Settings, then Personalization, select Taskbar, and expand Taskbar behaviors. Find the "Show smaller icons on the taskbar" option and set it to Always to reduce icon size and taskbar height. To revert to the default size, turn the option off.
Free Upgrade to Windows 11 Pro for Education (K-12) Command Prompt (Administrator) Log in with a local account, open Command Prompt as administrator, run the Clipupgrade.exe command, and authenticate with a K-12 organization account to confirm upgrade rights. The system will prepare the update and complete it after a restart. Reverting to Windows 11 Home requires a clean reinstall.

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