Windows Camera App Fails with Error 0xA00F4240 on Insider Build 26220.8680 While Webcam Works in Other Applications

This behavior matches a software issue in the camera stack/app on recent Insider builds rather than a hardware or basic driver problem, since the webcam works in OBS, browser tests, and at lower resolutions in Meet.

On Insider builds, the main options are to try the standard camera troubleshooting steps and, if those do not help, either roll back the problematic update or pause Insider updates and wait for a newer build that fixes the regression.

Try the following in order:

1. Verify camera privacy and app access
   1. Open Start > Settings > Privacy & security > Camera.
   2. Ensure Camera access is turned on.
   3. Ensure Let apps access your camera is turned on.
   4. In the list, confirm that the Camera app is allowed to use the camera.
   5. If using desktop apps (like browsers, Teams, etc.), make sure Allow desktop apps to access your camera is turned on as well.
2. Test the camera in the built‑in Camera app after a clean restart
   1. Restart the PC: Start > Power > Restart (do not just wake from sleep).
   2. After restart, open Start > Camera and see if the preview works.
   3. If the camera works here but not in other apps, the issue is with those apps’ settings; if it still fails with 0xA00F4240, continue.
3. Run the Camera troubleshooter (Windows 11)
   1. Use the Get Help app and run the camera troubleshooter from there:
      • Run the troubleshooter in Get Help
   2. Let it complete diagnostics and apply any fixes it suggests.
4. Update the camera driver from Device Manager
   1. Select Start > Device Manager.
   2. Expand Cameras and locate the internal webcam.
   3. Right‑click the camera > Update driver.
   4. Choose Search automatically for drivers so Windows can look for a newer or more compatible driver.
   5. Restart the PC and test the Camera app again.
5. Check for Windows and optional driver updates
   1. Go to Start > Settings > Windows Update > Check for updates.
   2. If available, select Advanced options > Optional updates and look for any camera or imaging device driver updates.
   3. Install any available updates and restart the device.
6. Confirm it is app‑specific Since the camera already works in OBS and browser tests, use that as confirmation that hardware is fine. If the Camera app continues to show a gray preview and 0xA00F4240 while other apps still work, this strongly indicates a regression in the Camera app or media pipeline in that Insider build.
7. Insider‑specific mitigation If none of the above resolves the issue and it only occurs on this Insider build:
   • Keep the Feedback Hub report updated with any new observations (e.g., that 720p fails in Camera but works in OBS), so it can be correlated with other reports.
   • Consider pausing Insider updates until a newer build is released that may contain a fix.
   • If the issue started exactly after installing a specific cumulative update for this build and there is an uninstallable KB (similar to how some users fixed app issues by uninstalling KB5079491), you can try uninstalling that update from Settings > Windows Update > Update history > Uninstall updates and see if the Camera app starts working again.

Because this is an Insider Preview build, if the standard troubleshooting (privacy, troubleshooter, driver update, Windows Update) does not fix the problem, the remaining realistic path is to wait for a newer build or revert/clean‑install a known‑good build where the Camera app works.

References:

• Camera doesn't work in Windows
• my camera does not function in windows - Microsoft Q&A
• can you fix update 26220.8138 insider preview - Microsoft Q&A