hdr-always-on

Keep HDR enabled on your external displays. Runs silently in the background on macOS.

The problem

macOS often disables HDR on external displays after sleep, unlock, or display reconnection. There's no built-in way to keep it on -- the only option is manually toggling it in System Settings > Displays every time.

How it works

Uses the macOS CoreDisplay private API to check and enable HDR on all connected external displays. No UI interaction, no dependencies beyond Python 3 (included with macOS).

Runs at login and every 15 minutes via launchd. When HDR is already on, the check takes milliseconds.

Install

Option 1: One-liner (recommended)

curl -fsSL https://raw.githubusercontent.com/nostitos/hdr-always-on/main/install.sh | bash

Option 2: Download the .pkg installer

Download the latest .pkg from the Releases page and double-click to install. No Terminal required.

Option 3: Git clone

git clone https://github.com/nostitos/hdr-always-on.git
cd hdr-always-on
bash install.sh

Uninstall

curl -fsSL https://raw.githubusercontent.com/nostitos/hdr-always-on/main/uninstall.sh | bash

Run manually

bash ~/.local/bin/enable-hdr.sh

Technical details

The script calls two private CoreDisplay framework functions:

• CoreDisplay_Display_IsHDRModeEnabled(displayID) -- check if HDR is on
• CoreDisplay_Display_SetHDRModeEnabled(displayID, true) -- turn it on

It enumerates all online displays via CGGetOnlineDisplayList, skips built-in displays, and enables HDR on every external display that supports it. Displays that don't support HDR are silently skipped (the API returns a non-zero error code).

Compatibility

• macOS: Tested on Sequoia 15.x (Apple Silicon). May work on earlier versions.
• Displays: Any external display with HDR support (LG, Samsung, Dell, Sony, etc.). The script is display-agnostic.
• Apple Silicon & Intel: Uses standard CoreGraphics/CoreDisplay frameworks available on both.

Caveats

• Uses a private API that Apple could change or remove in future macOS updates.
• The launchd job runs every 15 minutes on the clock (:00, :15, :30, :45). You can edit the plist to change the interval.

Logs

tail -f /tmp/enable-hdr.log

License

MIT