Backlight control with i3

Controlling the LED backlight brightness on a laptop in Linux used to be a chore, but most window managers automatically configure the brightness buttons on your laptop. However, everything is much more customizable in i3 and it requires a little more configuration.

Controlling the light #

First off, we need something that allows us to control the brightness. There’s a perfectly named project called light that does exactly this task! In Fedora, install it via:

$ sudo dnf -y install light

You can query the current brightness:

$ light -G
5.00

On my laptop, 5% is very dim. Now we can increase the brightness using a simple command:

$ light -A 5
$ light -G
9.99

And we can bring it right back down:

$ light -U 5
$ light -G
5.00

Setting up hotkeys #

Open your i3 configuration (usually ~/.config/i3/config) and add the hotkey configuration:

# Handle backlight.
bindsym XF86MonBrightnessUp exec light -A 5
bindsym XF86MonBrightnessDown exec light -U 5

Refresh the i3 configuration with $mod + shift + r.

Each time you press the brightness up button on your laptop, the brightness level goes up by 5%. The brightness down button lowers it by 5%. This is a good setup for me since I normally only need to adjust it by a few stops depending on ambient light.

However, if your lighting changes drastically from time to time, you can set up a different keybinding for a much more aggressive change:

# Handle backlight.
bindsym XF86MonBrightnessUp exec light -A 5
bindsym XF86MonBrightnessDown exec light -U 5
bindsym shift+XF86MonBrightnessUp exec light -A 25
bindsym shift+XF86MonBrightnessDown exec light -U 25

Hold shift and press brightness up or down. Now you are moving up and down by 25% brightness each time. Enjoy! 💡

Photo credit: Ariel on Unsplash