How to change external monitor brightness on a Mac
The brightness keys on a Mac change the built-in display, but most third-party monitors ignore them. You end up pressing the buttons on the monitor itself. Here is why, and how to change it from your Mac instead.
Why macOS can't dim most external monitors
A Mac controls its built-in display directly. An external monitor sets its own backlight, and the Mac has to ask it to change over a protocol called DDC/CI (Display Data Channel Command Interface). macOS doesn't use DDC/CI for brightness on most third-party monitors, so you need an app that does.
Apps that speak DDC/CI
- MonitorControl and Lunar are dedicated monitor apps with keyboard and menu bar controls. They are a good choice if you mainly want the brightness keys to work on your monitors.
- Haptiker adds brightness to your trackpad: slide along the left edge and it changes whichever screen your cursor is on, built-in or external.
External brightness with Haptiker
- Install Haptiker and allow Accessibility access.
- Move the cursor onto the external monitor.
- Slide one finger up or down the left edge of the trackpad.
Haptiker talks to each monitor over DDC/CI, so every display is adjusted on its own. This needs an Apple Silicon Mac. To see which monitors respond, open Settings › General › External displays.
If it doesn't work
- Check that DDC/CI is turned on in the monitor's own on-screen menu.
- Try a direct cable. Some adapters, docks and hubs don't pass DDC/CI through, and displays connected through DisplayLink often can't be controlled this way.
- Some monitors don't support brightness control over DDC/CI at all.
- On Intel Macs, Haptiker doesn't support external monitor brightness.
Still stuck? See Support, or read about trackpad volume and brightness.