03 / DISPLAYS · 6 min read
How to Control External Monitor Brightness on Mac
Why your Mac brightness keys do nothing on an external monitor, and what to check to get brightness control working.
The brightness keys on a Mac keyboard only control Apple displays. To change the brightness of another brand of monitor, use the buttons on the monitor itself, or an app that can send brightness control to external monitors. Make sure the monitor's own menu has external control turned on.
When you plug a non-Apple monitor into a MacBook or Mac mini, the brightness keys (F1 and F2) usually show a disabled symbol or only dim the laptop screen. Here is how to fix it.
Two ways to change brightness
- Real monitor brightness: the Mac tells the monitor to change its own backlight (this uses a standard called DDC/CI). It saves power and keeps colors accurate.
- Software dimming: the Mac darkens the picture on screen. It works on any monitor, but the backlight stays just as bright and contrast gets worse.
Checklist if brightness control does not work
- Turn on external control in the monitor menu. Use the buttons on the monitor to open its menu. Look for DDC/CI, External Control or something similar, and set it to On.
- Check your cable and hub. Some cheap USB-C hubs and HDMI adapters block brightness control. Try a direct USB-C to DisplayPort cable, or a good HDMI cable plugged straight into the Mac.
- Restart the monitor. Unplug its power cable for 10 seconds, then plug it back in.
Changing brightness with Tegaro
The Tegaro Displays tool lets you change the brightness of an external monitor from your keyboard with ⌃⌥ + and ⌃⌥ −. Displays stays free after the 14-day trial.
Whether brightness control works depends on your monitor and your cable. If the monitor or a hub does not allow it, no app can change that.
Frequently Asked Questions
Why do F1/F2 brightness keys not work on my Dell/LG monitor?
macOS only sends the brightness keys to Apple displays. For other monitors, you need to use the monitor's own buttons or an app such as Tegaro that controls external monitors.
Does HDMI support brightness control on Apple Silicon Macs?
Often yes when the monitor is connected directly, but some USB-C hubs and adapters block it. If it does not work, try a direct cable.
Which keys change external monitor brightness in Tegaro?
Press ⌃⌥ + to raise and ⌃⌥ − to lower the brightness of an external monitor.
Ten Mac tools, one icon
Tegaro puts Displays, Clipboard, Displays, Power and more in one menu-bar icon. Everything is free for 14 days, no card needed; after that the core tools stay free and Pro unlocks the rest.