Format guide
CMYK
Cyan Magenta Yellow Key color model
CMYK describes how much cyan, magenta, yellow, and black ink to lay down to produce a color on paper — each channel 0 to 100%. It's the print industry's color model because printers add ink (subtractive color) instead of emitting light (additive RGB). The same color almost always renders slightly differently on-screen vs in print because the gamut differs. Required by every commercial print shop and built into Photoshop's print prep workflow.
How to open a CMYK file
Adobe Photoshop, Illustrator, InDesign all natively work in CMYK mode (Image → Mode → CMYK Color). Affinity Photo, GIMP via plugins. Print-shop submission portals accept CMYK PDFs directly.
Primary use
Print-shop color specifications and prepress workflows.
Convert other formats to CMYK
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