Lumen

Lumen runs as a menu‑bar utility on macOS and adjusts the display’s brightness in real time according to the visual content of the active window. When a dark application such as a terminal is in focus, it raises the brightness; when a bright window like a web browser is active, it lowers the brightness, using the standard brightness keys for control while learning the user’s preferences automatically.

The tool is intended for macOS users who want a more comfortable viewing experience, especially in low‑light conditions, without relying on the system’s built‑in auto‑brightness feature. It requires screen‑recording permission to analyze the screen content and is not compatible with other brightness‑modifying services such as Night Shift or f.lux. External monitors are not supported directly, though third‑party utilities can synchronize their brightness with the laptop screen.

Installation is offered via Homebrew cask or direct binary download, and the project is released under GPL‑v3. Contributions are welcomed through feature requests, bug reports, and pull requests.