Adjustable brightness disable

The correct action depends on the display: use the monitor’s physical controls for an external screen, but repair the graphics driver if the disabled slider controls a laptop’s built-in display.

If this is an external monitor

Windows 11 commonly does not provide a working brightness slider for external monitors connected through HDMI or DisplayPort.

1. Open the monitor’s on-screen menu using its physical buttons or joystick.
2. Find Picture, Brightness, or Display, and adjust brightness there.

This is expected Windows behavior, not necessarily a fault. ^1^

If this is a laptop’s built-in display

Turning on automatic brightness should not disable manual adjustment; Windows still permits fine-tuning with the brightness slider. ^1^

Check whether Windows is using the correct graphics driver:

1. Right-click Start and select Device Manager.
2. Expand Display adapters.
3. Check the displayed adapter name.
4. If it says Microsoft Basic Display Adapter, visit the support page for your exact laptop model and reinstall the graphics driver supplied by its manufacturer.
5. Restart the computer, then open Settings → System → Display and test the brightness slider.

The Basic Display Adapter entry indicates that the proper graphics driver is absent, corrupt, or not being used. Reinstalling the manufacturer-provided driver is the documented resolution for this matching symptom. ^2^

If the correct graphics adapter is already listed

If the problem started immediately after a Windows or graphics-driver update, roll back that driver:

1. In Device Manager, expand Display adapters.
2. Right-click the graphics adapter and select Properties.
3. Open Driver → Roll Back Driver → Yes.
4. Restart Windows.

Administrator permission is required. If Roll Back Driver is unavailable, Windows has no previous driver stored; instead, download and reinstall the correct driver from the computer manufacturer. Microsoft also documents updating or uninstalling the display driver as subsequent recovery options. ^3^

After restarting, the expected result is an active slider under Settings → System → Display → Brightness.

References

1. [Windows 11](https://support.microsoft.com/windows/hardware/display-graphics/change-display-brightness-and-color-in-windows)
2. How to fix Brightness and Night Light not working issue on Windows 11 - Microsoft Q&A
3. [Windows 11](https://support.microsoft.com/windows/hardware/display-graphics/troubleshoot-screen-flickering-in-windows#fix-your-display-driver)