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What's new in the Windows 11 Insider builds for 25 September 2026

Affects
  • Windows 11, version 26H2
  • Build 26340.9577
PCDecoder Desk3 min read

Quick answer

The 25 September 2026 update introduces Build 26340.9577 to the Experimental channel, featuring a scrollable phone companion in the Start menu and new Energy Recommendations in Quick Settings. It also expands Narrator's math reading capabilities to six languages and improves USB audio device compatibility.

On 25 September 2026, Microsoft released Windows 11 Insider Experimental Preview Build 26340.9577. This update is part of the ongoing development cycle for Windows 11, version 26H2, delivered via an enablement package. As an Experimental channel release, this build is designed for tech enthusiasts who want to test new features early in their development lifecycle. Because these features are often in a state of flux, users should expect some rough edges and variable stability compared to the Beta or Release Preview channels. This update is particularly significant for users who rely on accessibility tools or power management features, as it introduces targeted refinements to both areas.

For those unfamiliar with the Windows Insider Program, Experimental builds are the earliest versions of Windows released to the public. They are ideal for users who want to help shape the future of the operating system by providing feedback on new concepts. However, because these builds are not yet finalized, features may change, be removed, or be replaced entirely before they reach the general public. A visible watermark in the lower-right corner of your desktop is a standard indicator that you are running a pre-release build, and this is entirely normal behavior for these versions of Windows 11.

Highlights

  • The phone companion within the Start menu has been updated to show more of your recent activity, now featuring a scrollable side pane so you can view extensive content without needing to open a separate application.
  • Energy Recommendations are now accessible directly within Quick Settings, allowing users to discover and implement power-saving actions to improve device sustainability without navigating deep into the main Settings menu.
  • The temporary files section under Settings > System > Storage has received minor visual refinements to improve clarity and design consistency.
  • Narrator math reading support has been expanded to six languages, including English (United States), English (United Kingdom), Traditional Chinese, Finnish, German, and Spanish, which can be configured in Narrator settings.
  • Math reading functionality is now compatible with web content in Microsoft Edge Stable version 153.0.4234.32 and later, as well as Chrome Stable version 153.0.8010.18 and later.
  • A fix was implemented for an issue affecting certain USB Audio Class 1.0 devices, including specific multichannel audio headsets, which previously prevented them from functioning correctly after system updates.
  • The underlying state persistence for taskbar settings has been improved, ensuring that configurations remain stable when connecting or disconnecting multiple monitors.

Known issues

Microsoft reports no known issues for this update.

Should you install it?

If you are already enrolled in the Experimental channel of the Windows Insider Program, your device will likely receive this update automatically. This build is intended for enthusiasts and power users who are comfortable troubleshooting potential system instability. Because this is pre-release software, it is not recommended for your primary work machine or any device where you require absolute reliability. If you need a stable environment for daily tasks, you should stick to the Release Preview channel or the standard retail version of Windows 11.

If you are not currently an Insider, you should avoid installing this build unless you are prepared to perform a clean installation of Windows to revert to a stable state. Experimental builds are not meant for general users, and the potential for bugs or broken features is significantly higher than in standard monthly updates.

How to get it

  1. Open the Settings app by pressing the Windows key + I on your keyboard.
  2. Navigate to Windows Update in the left-hand sidebar.
  3. Click on the Windows Insider Program menu item.
  4. Ensure your device is enrolled in the Experimental channel. If you are not enrolled, you will need to link your Microsoft account and select the Experimental channel from the available options.
  5. Return to the Windows Update page and click Check for updates.
  6. The system will download and install Build 26340.9577 automatically. You will need to restart your computer to complete the installation process.

If you are an IT professional or a developer, you can also check for these builds via the Microsoft Update Catalog, though the Windows Update method remains the standard path for most users.

Sources

Frequently asked questions

What is the Windows 11 Experimental channel?

The Experimental channel is for tech enthusiasts who want to test the earliest, most experimental features of Windows 11. It is the first place new ideas appear but often comes with lower stability.

How do I check my current Windows build number?

You can find your build number by pressing the Windows key + R, typing 'winver', and pressing Enter. A window will appear showing your current version and build information.

Can I switch from the Experimental channel to the Beta channel?

Yes, you can usually switch channels within the same Windows core version via Settings > Windows Update > Windows Insider Program, though some major core version changes may require a clean install.

What should I do if my USB headset stops working after an update?

First, ensure your system is fully updated. If the issue persists, check the manufacturer's website for updated drivers or use the Windows Device Manager to uninstall and reinstall the audio device.

Checked against Microsoft's release notes on ; re-checked when a new build ships.

Written by

PCDecoder Desk

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