An open-source Mac utility that uses DDC/CI to remap the F1/F2 keys to actually move a third-party monitor’s hardware backlight, with the native macOS OSD overlay.
Plug a Dell, LG, or BenQ into a Mac and the F1/F2 keys do nothing. Apple reserves real brightness control for its own displays — every external panel is left at whatever level it shipped with, until you find the small joystick on the back and start poking at the manufacturer’s on-screen menu. MonitorControl fixes that by sitting in the menu bar, talking DDC/CI to the monitor over the existing video cable, and remapping Apple’s standard keys to actually move the panel’s hardware backlight.
It also slaves the external display to the laptop’s ambient-light sensor, so when the built-in panel dims at sunset, the LG next to it follows along. Volume keys can drive the monitor’s built-in speakers via the same DDC channel where supported. Per-monitor preferences live in a menu bar item with sliders that mirror what Apple ships natively — the OSD overlay that pops up when you press the keys is the same translucent slider, not a custom UI. Out of the box it covers the entire “I just want my keys to work” gap; advanced controls (gamma, color preset switching, software dimming as a fallback for monitors without DDC) are tucked into preferences for the people who need them.
Honest limitations: DDC/CI is a 1980s monitor protocol that some manufacturers implement worse than others, so a few panels will respond slowly or not at all to brightness changes. USB-C hubs can interrupt the DDC channel; the project’s GitHub issues track which docks pass it through cleanly. And on some Macs, sleeping the laptop briefly wakes the monitor at 100% before MonitorControl reasserts the saved level. None of these are deal-breakers — they’re the shape of what working with DDC actually looks like.
Free, GPL-licensed, brew-installable as brew install --cask monitorcontrol. The kind of utility that should ship in the OS and doesn’t — written by people who decided to fix that themselves a long time ago.