External display guide
Control external monitor brightness on macOS.
macOS does not expose every third-party monitor’s brightness controls in one place. Dimmerly puts per-display brightness, warmth, contrast, and supported monitor controls in the menu bar.
How hardware monitor control works
The direct-download build can communicate with compatible external monitors through DDC/CI. When the display and connection support it, Dimmerly can adjust the monitor’s hardware brightness and expose additional controls such as contrast, volume, mute, or input source.
Install the signed and notarized build from GitHub Releases, or install it with Homebrew:
brew tap olujicz/dimmerly
brew install --cask dimmerlyAfter connecting the monitor, open Dimmerly from the menu bar. A hardware indicator shows when a display is being controlled through DDC/CI.
Check these four things first
- Use the direct-download build when you need DDC/CI hardware controls. The sandboxed App Store build does not include them.
- Open the monitor’s on-screen menu and enable DDC/CI if the manufacturer provides that setting.
- When possible, connect the monitor directly to the Mac over USB-C or DisplayPort. A hub, dock, KVM, HDMI adapter, or DisplayLink adapter can block DDC/CI commands.
- Open the Dimmerly menu and expand the display row. If the hardware indicator is not present, the app is using software dimming for that display.
Connection support varies. A monitor can support DDC/CI while a particular adapter or dock does not pass the commands through. This is why the same display may work when connected directly but not through a dock.
When Dimmerly uses software dimming
Software dimming changes the image sent to the display through macOS’s gamma tables. It changes perceived brightness, but it does not change the monitor’s physical backlight. This fallback is useful for built-in displays and external monitors that do not expose usable DDC/CI controls.
The direct-download build can fall back to software dimming for a display when hardware control is unavailable. The App Store build uses the sandbox-compatible software controls and does not provide DDC/CI hardware control.
Direct download or App Store build?
Both builds provide the everyday display controls. Choose the direct build when external-monitor hardware control or display sleep is important.
| Capability | Direct download | App Store build |
|---|---|---|
| Brightness, warmth, and contrast | Yes | Yes |
| DDC/CI hardware monitor control | Supported displays and connections | No |
| Display sleep using macOS system tools | Yes | No |
| App Sandbox | No | Yes |
Still not seeing hardware control?
Try a direct connection, confirm DDC/CI in the monitor menu, and restart Dimmerly after changing the connection. If the hardware indicator still does not appear, read the troubleshooting guide or open a monitor compatibility issue with your display model and connection type.