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Introduction
If you’ve plugged an external monitor into your Mac and found that the brightness keys don’t work, you’re not alone. Most third‑party monitors don’t support Apple’s native DDC/CI brightness control, meaning your keyboard and Control Center sliders have no effect. But you still have several ways to adjust brightness on an external monitor connected to your Mac.
This guide covers every method, from physical monitor buttons to third‑party software that puts brightness control back on your keyboard. For the built‑in display, see our pillar how to adjust brightness on a Mac guide . For automatic brightness and True Tone, our auto‑brightness guide covers those features.
Method 1: Use the Monitor’s Physical Buttons
Every external monitor has physical controls—buttons on the bottom, back, or side that open an on‑screen display menu. Look for a brightness setting in that menu and adjust it manually. This is the most reliable method, but it’s slow if you frequently change brightness.
Method 2: Use MonitorControl (Free, Open Source)
MonitorControl is a free, open‑source Mac app that lets you control external monitor brightness and volume using the same keyboard keys as your built‑in display. It uses DDC/CI, a protocol built into most modern monitors, to send brightness commands.
- Download MonitorControl from GitHub (github.com/MonitorControl/MonitorControl).
- Install and open the app.
- Grant accessibility permissions when prompted.
- Your brightness keys (F1/F2) now control both your Mac’s display and your external monitor.
The app lives in your menu bar and works automatically once set up. It’s the closest thing to native support.
Method 3: Use Lunar (More Advanced)
Lunar is a paid app (4.99/monthor44.99 one‑time) that offers more advanced external brightness control, including adaptive brightness based on ambient light and scheduled brightness changes.
- Download Lunar from lunar.fyi.
- Follow the setup wizard to grant permissions.
- Lunar automatically detects your external monitor and maps brightness keys to it.
Lunar also supports Apple’s XDR displays and can sync brightness across all connected screens.
Method 4: Use DDC/CI Commands from Terminal
If you prefer the command line, install ddcctl via Homebrew (brew install ddcctl) and run:
text
ddcctl -d 2 -b 70 # Set display 2 brightness to 70%
This method is reliable but requires knowing your monitor’s DDC/CI address.
Method 5: Use the Apple Studio Display or Pro Display XDR
If you have an Apple display, brightness control works natively—the keyboard keys, Control Center, and System Settings all adjust it just like the built‑in MacBook screen. No third‑party software is needed.
Frequently Asked Questions
Why don’t my keyboard brightness keys work on my external monitor?
Most third‑party monitors don’t support Apple’s native brightness protocol. Use MonitorControl or Lunar to add this functionality.
Does MonitorControl work on Apple Silicon Macs?
Yes, MonitorControl is fully compatible with Apple Silicon and Intel Macs.
Can adjusting external monitor brightness from software damage the monitor?
No. DDC/CI is an industry‑standard protocol used by monitor manufacturers. It’s safe.
