Microsoft has released cumulative update KB5121158 (Build 28120.2824) for Windows 11 version 26H1, intended for insiders on the Experimental channel. This update includes a small set of general improvements and fixes designed to improve system performance. Changes are rolling out to insiders gradually, so they will not appear for everyone at the same time.
- Personalization. Improved stability of the Settings > Personalization > Background page. Added support for DIB format images as desktop wallpapers. Desktop slideshow now works more reliably on newly created accounts. Improved thumbnail resolution when selecting a background in Personalization > Background. Fixed wallpaper preview display in Settings on monitors with portrait orientation. Improved stability of wallpaper change processing when it occurs multiple times in a row. Slideshow now works with multiple desktops: the system no longer switches the background back to a single image. Fixed a bug from the previous build that caused wallpapers to turn black after every reboot for some insiders.
- Windows Recovery Environment. The Windows Recovery Environment (WinRE) can now connect to Wi-Fi profiles saved in the system, including supported networks with certificate-based authentication. Previously, it only connected automatically to a wired network without authorization or to a Wi-Fi access point pre-configured separately for WinRE, and passwords for other WPA2 and WPA3 networks had to be entered manually. Now, if a recovery scenario requires internet access, the environment will use data from an already saved profile. This applies to quick machine recovery and cloud-based system rebuild: neither the user nor the administrator will have to pre-configure Wi-Fi credentials in WinRE. The feature is enabled by default, and administrators can disable it.
- Print Management. The updated print management interface has been temporarily removed from insider builds; Microsoft is refining it based on feedback. The previous print management tools remain in place and work as before. The company plans to bring back the new interface version in one of the future builds.
- File Explorer. The File Explorer Home page remembers the state of sections, whether expanded or collapsed, and opens in the same state it was left in.
- Magnifier. The Magnifier toolbar has received updated design: icons are aligned to the Windows 11 style, and padding and spacing have been adjusted. The behavior of the tool has not changed; viewing modes, zoom controls, keyboard shortcuts, and read-aloud work as before.
- Emoji. Added support for Emoji 17.0. Among the new symbols: a distorted face, a fight cloud, and a hairy creature. The emoji panel can be opened with Win + . (period). Some existing emojis have also been redrawn for consistency with other platforms.
You can install the update through Windows Update. To do this, go to Settings > Windows Update and click Check for updates. A computer restart will be required to complete the installation.
| Feature / Change | Performance Impact | Optimization | PC Speed | Gaming Optimization |
|---|---|---|---|---|
| Settings > Personalization > Background stability improvement | 🟢 Slight improvement (reduced UI hangs) | 🟢 Better memory handling for wallpaper previews | 🟡 Minimal (faster settings navigation) | ⚪ No direct impact |
| DIB format support for desktop wallpapers | ⚪ No measurable change | 🟢 Broader format compatibility | ⚪ No impact | ⚪ No impact |
| Desktop slideshow reliability on new accounts | 🟢 Slight improvement (less background re-processing) | 🟢 Reduced redundant wallpaper reloads | 🟡 Minimal (smoother login experience) | ⚪ No impact |
| Improved thumbnail resolution in Background settings | 🟡 Slightly higher thumbnail rendering cost | ⚪ Neutral | ⚪ No impact | ⚪ No impact |
| Wallpaper preview fix for portrait monitors | ⚪ No measurable change | 🟢 Correct preview scaling | ⚪ No impact | ⚪ No impact |
| Wallpaper change stability (multiple rapid changes) | 🟢 Reduced transient CPU/GPU spikes | 🟢 Better change queue handling | 🟡 Minimal (fewer explorer freezes) | ⚪ No impact |
| Slideshow with multiple desktops | 🟡 Slightly higher memory usage (per-desktop wallpapers) | 🟢 Correct per-desktop wallpaper state | ⚪ No impact | ⚪ No impact |
| Black wallpaper after reboot bug fix | 🟢 Slight improvement (removed faulty reload path) | 🟢 No more redundant fallback rendering | 🟡 Minimal (faster desktop ready state) | ⚪ No impact |
| WinRE saved Wi-Fi profile support | 🟢 Faster recovery network connection | 🟢 Reuses existing credentials | 🟢 Noticeable in recovery scenarios (less manual setup) | ⚪ No impact |
| Print Management updated interface removal | 🟢 Slight improvement (removed unfinished UI overhead) | 🟡 Neutral (reverted to stable tools) | ⚪ No impact | ⚪ No impact |
| File Explorer Home section state memory | 🟢 Slight improvement (less UI re-rendering) | 🟢 Persistent layout state | 🟡 Minimal (faster navigation) | ⚪ No impact |
| Magnifier toolbar redesign | ⚪ No measurable change | 🟡 Cosmetic alignment only | ⚪ No impact | ⚪ No impact |
| Emoji 17.0 support + redrawn emojis | 🟡 Slightly higher font/emoji rendering cost | 🟢 Broader symbol set | ⚪ No measurable impact | ⚪ No impact |
Official announcement on the Microsoft website.
The last 10 Windows updates:
| Update | Build | Version | Windows | Channel | Date |
|---|---|---|---|---|---|
| KB5126657 | 19045.7807 | 22H2 (ESU) | Windows 10 | Stable | 2026-10-13 |
| KB5126653 | 22631.7652 | 23H2 | Windows 11 | Stable | 2026-10-13 |
| KB5127646 | 28000.3231 | 26H1 | Windows 11 | Stable | 2026-10-13 |
| KB5127648 | 26300.9711 | 26H2 | Windows 11 | Stable | 2026-10-13 |
| KB5127757 | 28120.3181 | 26H1 | Windows 11 | Experimental | 2026-10-07 |
| KB5127758 | 26220.9606 | 25H2 | Windows 11 | Beta | 2026-10-07 |
| KB5127754 | 28020.3172 | 26H1 | Windows 11 | Beta | 2026-10-07 |
| KB5127753 | 26340.9616 | 26H2 | Windows 11 | Experimental | 2026-10-07 |
| KB5124192 | 28120.3151 | 26H1 | Windows 11 | Experimental | 2026-10-02 |
| KB5124196 | 28020.3142 | 26H1 | Windows 11 | Beta | 2026-10-02 |