ddcutil is a program for querying and changing monitor settings, such as brightness and color levels.

ddcutil primarily uses DDC/CI (Display Data Channel Command Interface) over I2C to communicate with monitors implementing MCCS (Monitor Control Command Set). Normally, the video driver for the monitor exposes the I2C channel as devices named /dev/i2c-n. Alternatively, there is support for monitors (such as Apple displays) that implement MCCS using a USB connection.

A particular use case for ddcutil is as part of color profile management. Monitor calibration is relative to the monitor color settings currently in effect, e.g. red gain. ddcutil allows color related settings to be saved at the time a monitor is calibrated, and then restored when the calibration is applied.

Detailed documentation for ddcutil can be found at www.ddcutil.com.