External monitor brightness slider for Windows

Where the external-monitor brightness sliders appear

Open Display Dimmer to use its display selector and Brightness slider. Installing the app does not add an external-monitor slider to Windows Settings or Quick Settings.

Windows' built-in slider usually controls a laptop panel. For the reasons it may be absent for an external display, see the Windows 11 external-monitor brightness slider missing guide. This page walks through using the app's controls.

Set up brightness control for your monitors

1. Install Display Dimmer from the Microsoft Store and open it from the Start menu.
2. Choose a display from the list at the top of the main window. Start with one monitor so you can check its response separately.
3. Open Settings → Displays. Keep Brightness control enabled on for each display you want the app to adjust. Disabled displays are excluded from All displays adjustments.
4. Choose its brightness method. Turn on Use hardware brightness (DDC/CI) for a compatible external monitor, and enable DDC/CI in that monitor's own menu. Leave the app's hardware switch off to use software gamma brightness. Switch changes take effect immediately in newer versions; select Apply if your version requires it.
5. Return to the main window and move Brightness a small amount. Check the selected screen. For hardware control, compare its brightness value in the monitor menu as described in the DDC/CI verification guide.

Each display can use its own method. A directly connected monitor might use hardware brightness while a monitor behind an incompatible dock uses software dimming. For a built-in laptop panel, lower hardware brightness using Windows or the laptop’s brightness keys, then use Display Dimmer for software dimming. Test software mode separately with HDR on, because gamma behavior can vary.

Example: two monitors, two brightness levels

Suppose you want a brighter work monitor and a darker secondary screen. These are example settings to try, not measured brightness targets:

Matching percentages do not guarantee matching appearance across different monitors or control methods. Adjust each screen by eye for your room. If a screen stays too bright at its hardware minimum, follow the below-minimum software-dimming steps.

Adjust All displays or reset the selected screen

Select All displays when you want one brightness gesture to affect all enabled displays. A display whose brightness control is disabled in Settings → Displays is left out.

Under Settings → General, Use relative brightness for grouped display sliders changes how this works. With it off, All displays applies the same app percentage to each enabled screen. With it on, displays with different starting brightness levels can be adjusted relatively instead of replacing their levels with one identical percentage.

Reset levels returns the selected display's app controls to Brightness 100%, Contrast 50%, and neutral temperature. With All displays selected, it resets all enabled displays. In hardware mode this can raise the monitor's own brightness; in software mode it removes the app's dimming without raising the monitor's manually set hardware brightness.

Reset levels saves these neutral levels. It is not Resume automation, and it can interrupt an active schedule or app rule when the reset conflicts with its settings.

For warmer screen colors, see the blue light filter and color temperature guide.

Choose hardware brightness or software dimming

The Brightness slider uses one of these methods for each display. Read DDC/CI versus gamma dimming for the differences and limitations.

Common setup problems

• A monitor is not available for adjustment: check that Windows recognizes it and that Brightness control enabled is on for that display in the app.
• Hardware mode does not respond: confirm DDC/CI is enabled in the monitor menu, then test a direct connection without the dock, adapter, or KVM.
• Only a docked monitor fails: video can work while DDC/CI commands are blocked. Follow the USB-C dock guide to compare the connection paths.
• Software mode does not change the image: test with HDR temporarily off. HDR and graphics-driver behavior can limit gamma dimming.

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