Build 26340.9502: Windows Insider Experimental Channel, September 2026. Magnifier contrast themes and Cloud rebuild drive sanitizing

Adds Magnifier contrast themes and new Cloud rebuild options, and fixes Plan9 folder sharing with Linux VMs and File History backups.

Does it affect you? Applies to: Devices enrolled in the Windows Insider Program in the Experimental Channel.

This is a test build for people in the Windows Insider Program. Features in it can change, be removed, or never reach regular Windows releases.

What changes

Gradual rollout

For: Insiders in the Experimental Channel

The Mouse indicator gets a new animation and can stay active until you press Esc.¹

Gradual rollout

For: Insiders in the Experimental Channel

A toolbar toggle applies a contrast theme to reduce glare while photos, videos, and charts keep their original colors. You can choose the theme in Magnifier settings; color inversion remains available separately.²

Gradual rollout 2 items

Cloud rebuild can erase drive data before Windows is reinstalled. Choose Remove files if keeping the PC, or Remove & sanitize files before recycling, returning, or reassigning it; sanitizing is irreversible.³
The sanitize option uses the storage hardware's erase capability.
IT administrators can configure and start a Cloud rebuild remotely, using the installed build or a target build they specify.⁴
This uses the Recovery CSP.

Gradual rollout

For: Insiders in the Experimental Channel

A new setting, off by default, keeps Live Captions from transcribing screen-reader audio, so captions focus on microphone and system audio.⁵
The setting excludes audio from screen readers such as Narrator, JAWS, and NVDA when off.

Folders shared from a Windows host with Linux VMs using Plan9 appear and can be accessed in the guest again.⁶
Fixes an issue affecting some applications that use HCS-managed virtual machines and share host folders with Linux VMs using Plan9.

For: File History users

Data sheet · Security · Downloads · Components Click to collapse or expand

Version	Build	Channel
—	26340.9502	Experimental Channel

No vulnerabilities are listed for this update.

Updated Oct 26, 2026

Cited passages from Microsoft's official notes (7)

1. We've also added the option to keep the indicator activated until you press the Esc key. learn.microsoft.com
2. With this update, we're introducing a new contrast theme toggle in Magnifier. learn.microsoft.com
3. The sanitize option uses the storage hardware's erase capability to securely erase data before Windows is reinstalled and is irreversible. learn.microsoft.com
4. IT administrators can now configure and start a Cloud rebuild remotely through the Recovery CSP, using either the currently installed build or a target build you specify. learn.microsoft.com
5. With the setting off, Live Captions won't transcribe audio from screen readers such as Narrator, JAWS, and NVDA, keeping captions focused on microphone and system audio. learn.microsoft.com
6. Folders shared from the Windows host using Plan9 didn't appear or couldn't be accessed in the guest environment. learn.microsoft.com
7. Fixed an issue where backing up using File History unexpectedly failed with an error saying, "No usable drives found." learn.microsoft.com

Checked automatically: 8 of 8 checks passed, 7 quoted passages

A second AI read the text against the sources: correctness 5/5, clarity 5/5, completeness 5/5. How we work

Published by The Update Bureau. Written with AI from Microsoft's own documents, checked by rules and a second AI. How we work · Report a mistake