UX/UI · Accessibility

Contrast checker

Pick the text and background colors. The tool calculates the contrast ratio and shows whether it passes WCAG levels AA and AAA.

Large sample text This is a normal paragraph used to evaluate contrast legibility at body size.
Contrast ratio 21 : 1

Contrast is accessibility, not aesthetics

Low-contrast text excludes people: those with low vision, color blindness, and anyone reading on a screen in sunlight. WCAG defines a minimum contrast ratio between text and background — the higher, the more legible.

The thresholds: normal text needs 4.5:1 for level AA and 7:1 for AAA. Large text (from ~18.66px bold or ~24px normal) can use 3:1 (AA) and 4.5:1 (AAA). UI components and essential icons need at least 3:1.

This calculation follows WCAG's official relative luminance formula and runs in your browser. It solves the contrast criterion — full accessibility involves much more (keyboard, screen readers, semantic structure), so treat this as a first filter.

Frequently asked questions

What are WCAG levels AA and AAA?

They are color-contrast criteria from the WCAG accessibility guidelines. AA is the recommended minimum for most text; AAA is stricter. The tool shows whether the color combination passes each level.

Does passing contrast guarantee full accessibility?

No. Contrast is an important part, but full accessibility involves other factors (structure, keyboard, screen readers) and requires testing with people and assistive technologies.

Is the tool free?

Yes. It's part of the EduBuilders Toolbox, a collection of free tools for instructional designers, L&D professionals and educators. No sign-up, no login.

What is EduBuilders?

EduBuilders is an educational-product studio working at the intersection of education, technology and AI. Besides building digital learning products, it maintains the EduBuilders Toolbox: free tools made by someone who actually works in Instructional Design.

Who is Ivan Chagas?

Ivan Chagas is an instructional designer, educational-product builder and founder of EduBuilders. He has worked in education since 2012, at the intersection of instructional design, artificial intelligence and learning technology, and built these tools to solve real problems for course builders.