Color Contrast Checker (WCAG)

What is a Color Contrast Checker?

A color contrast checker measures how distinguishable text is from its background by calculating the contrast ratio between the two colors. Sufficient contrast is essential for readability, especially for users with low vision or color blindness, and it is a core requirement of web accessibility guidelines.

Our Color Contrast Checker computes the exact contrast ratio using the official WCAG formula and tells you whether your color pair passes Level AA and Level AAA for both normal and large text, with a live preview so you can see the result in context.

Understanding WCAG Contrast Levels

• AA normal text — requires a ratio of at least 4.5:1
• AA large text (18pt+ or 14pt bold) — requires at least 3:1
• AAA normal text — requires at least 7:1
• AAA large text — requires at least 4.5:1
• Higher ratios mean more readable, more accessible text

How to Use the Checker

Choose your text color and background color with the pickers or by entering hex codes. The tool instantly calculates the contrast ratio and shows pass/fail badges for each WCAG level. The live preview renders sample text in your chosen colors so you can judge readability for yourself.

If a combination fails, try darkening the text, lightening the background, or increasing saturation differences until the ratio meets the level you are targeting.

Why Contrast Matters

Around one in twelve men and one in two hundred women have some form of color vision deficiency, and many more users browse in bright sunlight or on low-quality screens. Meeting WCAG contrast requirements makes your content readable for all of them. It is also a legal accessibility requirement in many jurisdictions, so checking contrast protects both your users and your organization.

Key Features at a Glance

• Calculates the exact contrast ratio using the official WCAG formula
• Pass/fail badges for AA and AAA, normal and large text
• Live preview renders sample text in your chosen colors
• Pick colors visually or enter hex codes directly
• Instant recalculation as you adjust either color
• Runs in your browser — private, offline-capable, and free

How Contrast Ratio Is Calculated

Contrast ratio is not a simple difference between two colors — it is based on relative luminance, a measure of how much light each color emits as perceived by the human eye. The formula weights the red, green, and blue channels differently because our eyes are most sensitive to green and least to blue, then compares the lighter color's luminance to the darker one's. The result is a ratio from 1:1 (identical colors, invisible) up to 21:1 (pure black on pure white).

Because luminance is perceptual rather than purely numeric, two color pairs with the same raw color distance can have very different contrast ratios. This is why a checker is essential: eyeballing contrast is unreliable, especially with mid-tone colors or saturated hues. The tool does the math precisely so you can trust the pass/fail result rather than guessing whether your text is readable enough.

Tips for Passing WCAG Contrast

• If a pair fails, darken the text or lighten the background in small steps
• Large or bold text has a lower threshold — use it for borderline cases
• Avoid placing colored text on a similarly colored background
• Test your real font weight, since thin fonts need more contrast to read
• Aim for AAA on body text where you can — it benefits every reader

Why Choose Our Color Contrast Checker?

Our contrast checker is free with no signup, no limits, and no subscription. It runs entirely in your browser, so results are instant, the tool works offline, and your color choices stay private — nothing is uploaded to a server.

It is one of more than 200 free tools on ToopTools, and you can pin it to your My Workspace, a personalized workspace where you keep the tools you use most in a single dashboard. Sitting beside the color picker and palette generator, the contrast checker lets you verify accessibility the moment you choose colors, without breaking your design flow.

Common Use Cases

Web developers and designers use the checker to make sure text, buttons, and links meet accessibility standards before shipping, avoiding the most common WCAG failure: insufficient contrast. Teams building design systems use it to validate every text-on-background combination in their palette up front.

It is also valuable for audits and compliance work. Many organizations are legally required to meet accessibility standards, and contrast is one of the most frequently cited issues. Running color pairs through the checker provides a clear, defensible pass/fail record. Content creators styling presentations, emails, or graphics use it to keep their text legible for every audience.

Is the Color Contrast Checker free?

Yes. It is completely free with no account, no sign-up, and no usage limits. Check as many color combinations as you need at no cost.

What contrast ratio do I need to pass WCAG?

Level AA requires at least 4.5:1 for normal text and 3:1 for large text. Level AAA requires 7:1 for normal text and 4.5:1 for large text. The checker shows whether your pair meets each of these thresholds.

What counts as large text?

WCAG defines large text as at least 18pt (about 24px) for regular weight, or 14pt (about 18.66px) for bold. Large text has a lower contrast requirement because bigger glyphs are easier to read.

Why does contrast matter for accessibility?

Low contrast makes text hard or impossible to read for people with low vision, color vision deficiency, or anyone using a screen in bright light. Meeting contrast requirements keeps your content readable for the widest possible audience.

Does the checker work for both text and UI elements?

Its ratios apply directly to text against its background. The same numbers are a useful guide for UI components like icons and borders, though WCAG sets a separate 3:1 minimum specifically for non-text interface elements.

Are my colors kept private?

Yes. All contrast calculations run locally in your browser, so your colors are never sent anywhere. The tool is private and works without an internet connection.

How do I check if two colors have enough contrast?

Enter your text color and background color and the tool instantly calculates the contrast ratio and shows whether it passes WCAG AA and AAA for normal and large text. Adjust either color until you reach a passing ratio.

Does the color contrast checker work offline?

Yes. The contrast ratio is calculated entirely in your browser, so once the page has loaded the tool works without an internet connection, and your colors are never uploaded. You can check accessibility privately on your own device.