Brightness control for Windows 11

Quick Settings

Click the group of status icons at the right of the taskbar — network, sound and battery act as a single button — or press Windows + A. The brightness slider sits at the top of the panel that opens. On a laptop it takes effect immediately; on a desktop with no controllable display, the slider is not shown at all.

Settings, and the options hidden under the arrow

Go to Settings › System › Display. The same slider appears under Brightness & colour, but here it has an expander arrow next to it, and the options underneath are the ones that cause most complaints:

• Change brightness automatically when lighting changes — the ambient light sensor. Only appears on devices that have one. Leave it off if you want a value that stays put.
• Change brightness based on content — content adaptive brightness control, done by the panel itself. It dims during dark scenes and brightens for white documents, and on some laptops it is aggressive enough to look like a fault. Set it to Off rather than Always or On battery only.
• Help improve battery by optimising the content shown — the same idea under a different name on some builds.

Keyboard keys

Laptop brightness keys are usually on the function row and may need the Fn key depending on how the firmware is configured. They depend on the manufacturer's utility being installed — a clean Windows install on a machine that shipped with a vendor package will often have working display drivers but dead brightness keys until that package is restored.

External displays

Recent Windows 11 releases added a setting that lets the system drive brightness on external monitors over DDC/CI, shown in the Display settings when a compatible monitor is connected. It works well on monitors that implement the protocol cleanly, and does not appear at all on those that do not — so its absence is a hardware answer rather than a Windows fault.

Where it is missing, the options are the monitor's own buttons or a third-party utility. See external monitors for the diagnosis, and compare for the tools.

HDR changes the meaning of the slider

With HDR turned on, the brightness slider no longer controls the panel directly. Instead, SDR content brightness under Settings › System › Display › HDR sets how bright ordinary windows and text appear relative to HDR highlights. If your desktop looks washed out or dim only in HDR mode, that is the control to move.