BrightKey — brightness keys for external displays

Make the Mac brightness keys control whichever screen the cursor is on, external displays included

Problem

Once a MacBook is docked to an external display, the keyboard brightness keys only change the built-in screen; dimming the external one means reaching for the OSD buttons behind the monitor and digging through menus. A developer took over the brightness keys inside their window manager specifically to fix this, which shows it is a daily, small, unsolved annoyance that currently only lives as a side feature.

Solution

A tiny menu bar app that intercepts the brightness and volume keys, decides the target by cursor position, drives external displays over DDC/CI, and shows a translucent system-style OSD. Handles multiple displays across brands and supports custom shortcuts.

Users

Developers, designers and remote workers running a MacBook with one or more external monitors

MVP

Cursor-position target selection; DDC/CI brightness control and key interception; system-style OSD; multi-display mapping config; compatibility notes for common brands

Revenue

$9.9–14.9 lifetime license with a free trial limited to a single external display; affiliate deals with monitor brands

Why now

Docking to external monitors is now the default Mac workflow and Apple still hasn't shipped this; DDC/CI libraries are mature, so a prototype is a one-week build