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MonitorControl v4.3.3
Control your external monitor brightness and volume from your Mac keyboard.
MonitorControl lets you adjust the brightness and volume of external displays using the same keys you use for your built-in screen. No more fumbling with physical monitor buttons — it syncs brightness via DDC/CI and volume via software control. It lives silently in your menu bar and supports multiple monitors. Free, open-source, and one of those tools you install once and forget is even there — until you use a Mac without it.