Why is the K in CMYK called key instead of black?

K stands for the key plate, the plate that prints outlines and text more precisely than the three colored inks manage alone. Using one black ink also cuts ink use and drying time. For large dark areas, printers layer cyan, magenta, and yellow under black, which is called rich black.

What's the difference between CMYK and Pantone colors?

CMYK is process printing: four inks halftoned together to approximate almost any color. Pantone is a spot-color system: a single premixed ink delivers one exact, repeatable color. Choose spot color when an exact brand color matters more than cost; some presses combine both.

Can I use CMYK values on a website?

No. Screens build color from red, green, and blue light, and browsers take RGB-based values like hex codes. Keep a CMYK version of your brand palette in your design files for print jobs, and use hex or rgb() values on the site itself.

Back to Web Design Glossary

What is CMYK?

Cyan, Magenta, Yellow, and Key (CMYK) is the subtractive color model used in color printing. Printers layer tiny halftone dots of these four inks on white paper; each ink absorbs light, so more ink means a darker color. Key is the black ink, named for the key plate that prints text and fine detail.

More About CMYK

Cyan, magenta, and yellow are the primary colors of pigment. Printers add black (the K, or key) as a fourth ink because mixing the other three at full strength produces only a dark, imperfect black, while a dedicated black ink prints sharper text, gives more consistent dark tones, and costs less. The RGB (red, green, and blue) color model works the opposite way: it mixes light instead of ink, and combining all three primaries at full strength makes white.

How CMYK printing works

CMYK is a subtractive model. The white in a printed image is the paper itself, and each ink absorbs (subtracts) part of the light reflecting off it, so more ink means a darker color and no ink means white.

A press can't blend inks the way a screen blends light, so it uses halftoning: tiny dots of the four inks, varied in size and spacing, that read as smooth tones at normal viewing distance. About 20% magenta coverage looks pink rather than light magenta. Without halftone dots, solid layers of the three colored inks could produce only 8 colors: cyan, magenta, yellow, red, green, blue, a dark near-black from all three, and the white of the paper.

A CMYK value is written as four ink percentages from 0 to 100. For example, 100/0/0/0 is pure cyan, 0/100/100/0 is red, and 0/0/0/100 is plain black.

CMYK vs. RGB

CMYK is the color model for print; RGB is the color model for screens.

Side-by-side comparison of the two color models: on the left, overlapping cyan, magenta, and yellow ink circles combine toward black, showing that CMYK is subtractive; on the right, overlapping red, green, and blue light circles combine toward white, showing that RGB is additive. The opposite center colors illustrate why print and screens need different color models.

CMYK: ink pigments on paper. Subtractive, so colors combine toward black. It's the standard model for color printing.
RGB: emitted light. Additive, so colors combine toward white. Use it for anything viewed on a screen; on the web, RGB colors are usually written as hex codes.

Converting RGB designs for print

Screens can display a wider range of colors (a larger gamut) than CMYK inks can reproduce, so vivid on-screen colors, especially neon greens and bright blues, come out duller when a file is converted for print. That shift is a limit of ink on paper, not a defect in your software.

Before you convert anything, ask the printer what file format and color profile it wants. Some print shops supply an ICC profile, a file that describes a specific printing device, and want a CMYK file converted to it before you send anything; others, including many photo labs and online print services, ask for RGB files and handle the conversion in their own workflow.

When a printer does ask for CMYK, convert a copy of the file in your design program using the profile the printer supplies; colors the inks can't reproduce shift to the nearest match they can. Keep your RGB master untouched, and order a printed proof before a full run whenever color accuracy matters.

When a website owner needs CMYK

Only when a design leaves the screen.

Work in RGB and hex for anything viewed on a screen: your website, social graphics, email, and digital ads.
Plan for CMYK when the design will be physically printed: business cards, brochures, packaging, and signage. Check the printer's file and color-profile requirements before you convert, since many services want RGB files and convert in-house.
Keep logos and brand colors in a master file with both RGB and CMYK values, so the brand stays as consistent as each medium allows. When an exact match matters, order a printed proof or specify a spot color.

Frequently Asked Questions

: K stands for the key plate, the plate that prints outlines and text more precisely than the three colored inks manage alone. Using one black ink also cuts ink use and drying time. For large dark areas, printers layer cyan, magenta, and yellow under black, which is called rich black.
: CMYK is process printing: four inks halftoned together to approximate almost any color. Pantone is a spot-color system: a single premixed ink delivers one exact, repeatable color. Choose spot color when an exact brand color matters more than cost; some presses combine both.
: No. Screens build color from red, green, and blue light, and browsers take RGB-based values like hex codes. Keep a CMYK version of your brand palette in your design files for print jobs, and use hex or rgb() values on the site itself.

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