zmk/docs/docs/config/backlight.md

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Backlight Configuration	Backlight

See the backlight feature page for more details, including instructions for adding backlight support to a board.

See Configuration Overview for instructions on how to change these settings.

Kconfig

Definition file: zmk/app/Kconfig

Option	Type	Description	Default
CONFIG_ZMK_BACKLIGHT	bool	Enables LED backlight	n
CONFIG_ZMK_BACKLIGHT_BRT_STEP	int	Brightness step in percent	20
CONFIG_ZMK_BACKLIGHT_BRT_START	int	Default brightness in percent	40
CONFIG_ZMK_BACKLIGHT_ON_START	bool	Default backlight state	y
CONFIG_ZMK_BACKLIGHT_AUTO_OFF_IDLE	bool	Turn off backlight when keyboard goes into idle state	n
CONFIG_ZMK_BACKLIGHT_AUTO_OFF_USB	bool	Turn off backlight when USB is disconnected	n

:::note The *_START settings only determine the initial backlight state. Any changes you make with the backlight behavior are saved to flash after a one minute delay and will be used after that. :::

Devicetree

Applies to: /chosen node

Property	Type	Description
zmk,backlight	path	The node for the backlight LED driver to use

See the Zephyr devicetree bindings for LED drivers:

• gpio-leds
• pwm-leds

See the backlight feature page for examples of the properties that must be set to enable backlighting.