BrightnessControl

One slider for every screen on your desk.

BrightnessControl is a free Mac menu bar app that sets the brightness of your built-in display and your external monitors. External screens are dimmed with their own backlight, not a grey overlay. It also switches your F1–F12 keys between media keys and function keys with fn + Esc.

Download for Mac Free. Apple Silicon, macOS 14 or later.
Displays
Built-in Retina Display
100%
LU28R55
62%
Function keys

Or press fn + esc anywhere.

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Try it: the top slider turns down this page. The link button moves both sliders together.

Function keys

An fn lock for your Mac. Press fn + esc anywhere to switch F1–F12 between media keys and standard function keys, or click the fn icon in the menu bar. It's the same setting as in System Settings, one keystroke away, and it applies immediately. Press esc here to try it.

Media keys

What it does

  • Real hardware brightness

    External monitors are set over DDC/CI, the same channel as the buttons on the monitor itself. Blacks stay black and the backlight draws less power.

  • Built-in and external, side by side

    Every connected screen gets its own slider, labelled with the name the monitor reports. Each slider covers exactly the range that monitor supports.

  • Link the sliders

    Turn on the link button and moving one slider brings every other screen to the same percentage. It stays on until you turn it off.

  • Out of the way

    No Dock icon, no window. Click the sun in the menu bar, set the level, move on. Plugging in a monitor shows its slider automatically.

Install

  1. Download the disk image

    BrightnessControl.dmg is always the latest version.

  2. Drag it into Applications

    Open the disk image and drag BrightnessControl onto the Applications folder.

  3. Open it the first time

    If macOS says it can't check the developer, open System Settings › Privacy & Security and click Open Anyway. You only need to do this once.

  4. Allow the fn + esc shortcut

    To use the shortcut, click Allow… on the Function keys card and turn on BrightnessControl under Privacy & Security › Accessibility. Everything else works without it.

  5. Start it at login, if you like

    Add it under System Settings › General › Login Items.

Requirements

  • A Mac with Apple Silicon (M1 or newer) running macOS 14 Sonoma or later. The glass look needs macOS 26.
  • A monitor with DDC/CI turned on. Most monitors support it; on some it's a setting in the on-screen menu.
  • Any keyboard for the function key switch. It flips the system-wide setting, so it applies to the built-in keyboard and Apple or third-party external keyboards alike.
  • A cable path that passes DDC through. USB-C, Thunderbolt and DisplayPort usually work. Some docks, hubs and HDMI adapters block it, and those monitors show “Brightness not readable”.

Questions

How do I change the brightness of an external monitor on a Mac?

macOS has no brightness control for most external monitors. BrightnessControl adds one: click the sun in the menu bar and move the slider for that monitor. It sends the change over DDC/CI, the same channel as the buttons on the monitor, so the backlight itself gets dimmer.

How do I switch F1–F12 between media keys and function keys on a Mac?

With BrightnessControl running, press fn + Esc anywhere, or click the fn icon in the menu bar. It flips the same setting as System Settings › Keyboard › "Use F1, F2, etc. keys as standard function keys", and the change applies immediately.

Is there an fn lock on a Mac?

Not as a key. macOS only has a setting in System Settings › Keyboard. BrightnessControl turns that setting into an fn lock: fn + Esc or one click on the menu bar icon switches between media keys and F1–F12.

Does BrightnessControl dim the screen with an overlay?

No. External monitors are set over DDC/CI and the built-in display through the same system path as the brightness keys. Blacks stay black and the backlight draws less power.

Why can't BrightnessControl change my monitor's brightness?

The monitor or the cable path doesn't pass DDC/CI through. Turn on DDC/CI in the monitor's on-screen menu, and connect over USB-C, Thunderbolt or DisplayPort. Some docks, hubs and HDMI adapters block DDC; those monitors show as not readable.

Why does the fn + Esc shortcut need Accessibility access?

macOS only lets apps with Accessibility access see key presses in other apps. BrightnessControl only reacts to fn + Esc and ignores every other key. Without access the slider and the menu bar icon still work.

Does BrightnessControl work on Intel Macs?

No. It needs a Mac with Apple Silicon (M1 or newer) and macOS 14 Sonoma or later.

Is BrightnessControl free?

Yes. It is free to download and use, with no account, ads or tracking. You can support it with a coffee.