How to change external monitor brightness on Mac

The brightness keys only change your MacBook’s screen. Change your external monitor too, from the menu bar.

Short answer

macOS adjusts built-in screens, Apple displays and some compatible displays. MacFixes adds a brightness slider for every connected display — the monitor’s own backlight where it accepts brightness commands, software dimming where it doesn’t.

What macOS gives you

The brightness keys and Control Center change built-in screens, Apple displays and some compatible displays. For most other monitors you use the buttons on the monitor itself.

How MacFixes fixes it

  1. 1
    Add the fix
    Open MacFixes Settings → Displays and add “Brightness for every display”. Fixes are off until you add them.
  2. 2
    Drag a slider
    Each connected display gets a brightness slider in the menu bar panel.
This is one of 28 fixes in MacFixes.
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Questions

Does it change the monitor’s real brightness?

On monitors that accept brightness commands over the cable (DDC/CI), yes. Displays that don’t are dimmed in software instead.

Does it work over HDMI?

Sometimes. Many HDMI ports and DisplayLink adapters don’t pass brightness commands; those displays are dimmed in software instead.

More fixes macOS doesn’t give you

Keep your Mac awake›Copy text from an image or anywhere on your Mac screen›Pick a colour from your screen›