Contrast in digital design is the difference in lightness (and sometimes color) between foreground and background. If body text is pale gray on white, many people can’t read it — in sunlight, with low vision, or with aging eyes.
WCAG sets minimum contrast ratios for text and UI components. Contrast is a core accessibility requirement, not a style preference — especially for people with color blindness, and in dark mode where a light-theme palette often fails. It also helps conversion: a CTA that blends into the page never gets tapped. Don’t rely on color alone to mean “required” or “error”; pair it with labels or icons.
A real-life example of contrast
A restaurant menu in tiny gold type on a cream photo looks elegant in a mockup and unreadable on a phone at lunch. Bumping the text to a dark color on a solid background is contrast work — the same fix as checking a button against WebAIM’s contrast checker.
Check contrast early, not as a last polish pass. It sits next to alt text and keyboard access in inclusive design — see How to Design an Accessible Website and Web Accessibility and Inclusive Design.