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External Monitor Brightness on Arch Hyprland

Why this is the standard​

  • External monitors do not use /sys/class/backlight → brightnessctl won't work
  • Wayland doesn't support xrandr brightness tricks
  • Only reliable way = hardware control via DDC/CI (I2C bus)

That's exactly what ddcutil does.

1. Core backend​

sudo pacman -S ddcutil i2c-tools
sudo modprobe i2c-dev
sudo modprobe i2c-nvidia-gpu

2. Permissions (required for smooth use)​

sudo groupadd i2c 2>/dev/null
sudo usermod -aG i2c $USER

Optional (proper fix):

echo 'KERNEL=="i2c-[0-9]*", GROUP="i2c", MODE="0660"' | sudo tee /etc/udev/rules.d/99-i2c.rules

3. Detect monitors​

ddcutil detect

4. Fast brightness control​

Use bus number (this matters a LOT for responsiveness):

ddcutil -b 2 getvcp 10
ddcutil -b 3 getvcp 10

ddcutil -b 2 setvcp 10 50
ddcutil -b 3 setvcp 10 50

ddcutil -b 2 setvcp 10 + 5
ddcutil -b 3 setvcp 10 - 5

Without -b, it's noticeably slower.

If fails without sudo:

sudo usermod -aG i2c $USER

Hyprland keybindings​

Add this to your custom config:

# Remove Omarchy's existing brightness bindings
unbind = CTRL, F1
unbind = CTRL, F2

# Rebind to external monitor brightness (DDC/CI)

# Decrease
bind = CTRL, F1, exec, ddcutil -b 2 setvcp 10 - 5 && ddcutil -b 3 setvcp 10 - 5

# Increase
bind = CTRL, F2, exec, ddcutil -b 2 setvcp 10 + 5 && ddcutil -b 3 setvcp 10 + 5

Notes:

  • unbind ensures Omarchy's Apple-specific brightness script does not run
  • Using && keeps both monitors in sync
  • LG → -b 2, MSI → -b 3

Optional refinements​

1. Faster response​

bind = CTRL, F2, exec, ddcutil -b 2 --sleep-multiplier=0.2 setvcp 10 + 5 && ddcutil -b 3 --sleep-multiplier=0.2 setvcp 10 + 5

2. Separate control per monitor​

# LG
bind = CTRL, F1, exec, ddcutil -b 2 setvcp 10 - 5
bind = CTRL, F2, exec, ddcutil -b 2 setvcp 10 + 5

# MSI
bind = CTRL SHIFT, F1, exec, ddcutil -b 3 setvcp 10 - 5
bind = CTRL SHIFT, F2, exec, ddcutil -b 3 setvcp 10 + 5