MacBright

A tiny menu bar app that boosts your MacBook Pro's display brightness past Apple's normal SDR cap, using the same EDR headroom that HDR content gets.

I wanted a free, minimal version of this that I could read every line of source for. So I made my own.

Disclaimer: This project was built with Claude Code (Opus 4.6).

What it does

On MacBook Pro models with the Liquid Retina XDR display (and other EDR-capable Apple displays), the panel can physically light up much brighter than what macOS uses for normal SDR content — that extra range is reserved for HDR video and photos. MacBright unlocks that headroom for everything on screen.

The result on an XDR MacBook is a noticeable, comfortable brightness bump on top of the system slider's max.

Install

Download a release

Grab the latest MacBright.zip from the Releases page, unzip it, and drag MacBright.app into /Applications.

On first launch, macOS will block the app with a Gatekeeper warning ("MacBright Not Opened" with only Done / Move to Bin buttons). On macOS 15 Sequoia and later there's no right-click bypass — you have to allow it from System Settings:

1. Try to open MacBright.app once (double-click it). You'll get the blocked dialog. Click Done.
2. Open System Settings → Privacy & Security.
3. Scroll down to the Security section. You'll see a line: "MacBright was blocked to protect your Mac."
4. Click Open Anyway next to it.
5. Authenticate with your password / Touch ID.
6. macOS will show one final confirmation dialog — click Open Anyway again.

You only need to do this once. After that, double-clicking works normally.

Why the warning? I don't pay for an Apple Developer Program membership ($99/yr), which means I can't sign or notarise the binary with an Apple-issued certificate. macOS therefore can't vouch for who built it. If you're not comfortable with that, clone the source, skim through it and build it yourself with the instructions below. I may get a developer license in the future.

Build from source

git clone https://github.com/langscot/macbright.git
cd macbright
make app
open .build/MacBright.app

Requires macOS 13+ and Xcode command line tools (for swift build).

Launch at login

Drag MacBright.app into System Settings → General → Login Items.

Updates

MacBright has no auto-update mechanism. Watch this repo (or check the Releases page) if you want to know when a new version ships.

Usage

MacBright lives in the menu bar — click the sun icon for the menu:

• Enabled — on/off toggle.
• Boost — slider from no boost (1.0×) to ~2.0× headroom.
• Only when plugged in — auto-disables on battery (default on, since boosting uses extra backlight power).
• Disable for current app — adds the frontmost app to an exclude list. Useful for HDR games and video players where the extra boost blows out highlights. Boost auto-disables whenever that app is frontmost and re-enables when you switch away.

There's no preferences window. If you want to change a setting that isn't in the menu, edit the source.

How it works

Two locks have to be picked at the same time:

1. EDR mode has to be active. macOS only lets the display run in its bright HDR-rendering mode when something HDR is on screen. MacBright keeps a 1×1 pixel CAMetalLayer window in the corner, set to wantsExtendedDynamicRangeContent = true and cleared to a high-EDR value. The mere presence of one bright EDR pixel is enough to keep the compositor in HDR mode for that display.

2. Every pixel needs to be told to use the extra range. Once EDR is active, the display's gamma table accepts output values above 1.0. MacBright writes a linear ramp from 0.0 to ceiling (where ceiling is configurable, max 2.0) via CGSetDisplayTransferByTable. Every pixel onscreen now gets multiplied through that ramp, and the >1.0 portion lands in the EDR backlight range.

To disable, MacBright calls CGDisplayRestoreColorSyncSettings() and tears down the EDR primer window. That's the entire mechanism.

Each lock alone is useless:

• Just the gamma write (without an active EDR surface) → values >1.0 get clamped, you get washout instead of brightness.
• Just the EDR window (without the gamma write) → only that 1×1 pixel is brighter, the rest of the screen is unchanged.

Both pieces use only public, documented Apple APIs — no private frameworks, no entitlements, no kernel extensions.

Battery impact

Designed to be cheap:

• The HDR primer renders one Metal frame on enable and never again until disabled. No display link, no per-frame work.
• The gamma table is written once on enable and once on disable.
• Power source detection is event-driven via IOPSNotificationCreateRunLoopSource — no polling.
• App-frontmost detection uses NSWorkspaceDidActivateApplicationNotification — no polling.

The dominant power cost is the backlight itself; the app process should sit at ~0% CPU/GPU when boost is active.

Architecture

Sources/MacBright/
  main.swift            # NSApplication entry point
  AppDelegate.swift     # creates menu bar + controller
  BoostController.swift # state machine: when to boost, when not to
  Brightness.swift      # the gamma table write + restore (GammaBoost)
  HDRPrimer.swift       # 1×1 EDR Metal window
  PowerMonitor.swift    # IOKit AC-power observer
  AppMonitor.swift      # frontmost app observer (for the exclude list)
  Settings.swift        # UserDefaults wrapper
  MenuBar.swift         # NSStatusItem + NSMenu UI

About 500 lines of Swift, no third-party dependencies, no private frameworks.

Compatibility

Designed and tested on a MacBook Pro (M-series, Liquid Retina XDR Display).

It should also work on:

• Pro Display XDR
• Studio Display
• Any other display where NSScreen.maximumPotentialExtendedDynamicRangeColorComponentValue > 1.0

On displays without EDR headroom (Air, older Pros, most external monitors), enabling MacBright just produces washout — there's no extra backlight to unlock. MacBright only ever touches built-in displays; external monitors are skipped on principle, since DDC-based external brightness is a totally different code path and would risk surprising users.

Credits

• TryAppleEDR — early proof-of-concept for EDR rendering that helped me understand the public API surface.
• Apple's WWDC21 talk Explore HDR rendering with EDR.

License

MIT — see LICENSE.