An image format that records pixel information using the additive colour model of combining amounts of cyan, magenta, yellow, and black to create a wide gamut of colours. This is based on the way standard web offset printing (SWOP) inks are combines on a press to create most printed colour documents.

In Graphic design when the final goal is to send something for SWOP printing it is oftin a good idea to work in CMYK as opposed to RGB to ensure a better colour match and to avoid problems when converting between the two systems further along in the pre-press process.