Color Contrast Checker
Color Contrast Checker is a free online tool that evaluates the contrast ratio between two colors to ensure they meet WCAG (Web Content Accessibility Guidelines) accessibility standards. Enter or pick two colors—foreground (text) and background—and the tool instantly calculates the contrast ratio, displaying whether the combination passes WCAG 2.1 Level AA or AAA requirements for normal and large text. Essential for web designers, developers, and content creators who need to ensure their text is readable by users with visual impairments or in challenging lighting conditions.
What Is
Color contrast is the difference in luminance (perceived brightness) between foreground text and its background. The Web Content Accessibility Guidelines (WCAG) 2.1 define minimum contrast ratios to ensure text is readable for people with visual impairments. WCAG Contrast Requirements: - Level AA (minimum): 4.5:1 for normal text (under 18pt/24px), 3:1 for large text (18pt+ bold or 24pt+ regular) - Level AAA (enhanced): 7:1 for normal text, 4.5:1 for large text - Non-text elements (icons, UI components): 3:1 against adjacent colors How contrast ratio is calculated: The formula is: (L1 + 0.05) / (L2 + 0.05) Where L1 is the relative luminance of the lighter color, and L2 is the relative luminance of the darker color. Relative luminance is calculated by converting sRGB values to linear light using gamma correction. Contrast ratio ranges from 1:1 (no contrast, same color) to 21:1 (maximum contrast, black on white). Why contrast matters: - 1 in 12 men have color vision deficiency - Aging reduces contrast sensitivity - Outdoor screen viewing requires higher contrast - Low vision users depend on high contrast - Legal requirements: ADA, Section 508, EN 301 549 The tool accepts any color format input and provides real-time feedback on compliance levels with clear visual indicators for pass/fail status.
How to Use
- Choose your foreground color (the text color) using the color picker, hex input, or by pasting any supported color format. Common choices include dark grays (#333333) or your brand color.
- Choose your background color using the same methods. This could be white (#FFFFFF), a light gray, or any background color used in your design.
- View the calculated contrast ratio displayed prominently. The tool shows both the numeric ratio (e.g., 7.23:1) and visual pass/fail indicators for each WCAG level.
- Check the WCAG compliance results: the tool displays whether your color combination passes AA and AAA for both normal text and large text. Green indicators mean pass, red means fail.
- Use the_adjust the lightness/darkness sliders to nudge your colors toward compliance while maintaining your design intent. Visual previews show how your text looks on the chosen background.
- Test multiple color variations quickly by swapping foreground and background colors with the swap button. Copy the final compliant color pair values for use in your CSS.
Examples
Input: Foreground: #000000, Background: #FFFFFF
Process: L1=1.0, L2=0.0 → (L1+0.05)/(L2+0.05)
Result: Contrast ratio: 21:1 (AAA pass for all sizes)
Input: Foreground: #767676, Background: #FFFFFF
Process: Relative luminance calc → Ratio formula
Result: Contrast ratio: 4.54:1 (AA pass, AAA fail normal text)
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Frequently Asked Questions
What is an acceptable contrast ratio for normal text?
For normal text (under 18pt bold or 24px regular), WCAG 2.1 Level AA requires a minimum contrast ratio of 4.5:1. Level AAA requires 7:1. If your ratio is below 4.5:1, you must darken the text or lighten the background. A ratio of 7:1 or higher satisfies both AA and AAA for normal text, providing the best accessibility.
Does contrast ratio change for large text?
Yes. Large text (18pt bold or larger, or 24pt regular or larger) has lower minimum contrast requirements: 3:1 for AA and 4.5:1 for AAA. This is because larger text is easier to read even at lower contrast. However, if your text can pass at 4.5:1, it's safer because users may not always view at expected sizes due to browser zoom or device differences.
Are there any exceptions to WCAG contrast requirements?
Yes. WCAG exempts: 1) Logos and brand names (no contrast requirement). 2) Decorative text that conveys no information. 3) Inactive/disabled UI elements. 4) Text in photographs or images (though alt text should be provided). However, if text conveys information, it must meet contrast requirements regardless of context.
Can I use a semi-transparent background to improve contrast?
Yes, but the calculation gets more complex. If your background is semi-transparent and sits over another color, the effective background color is the blend. The tool lets you account for alpha transparency by showing the blended result. The final perceived color (after alpha compositing) is what matters for contrast calculations.
How do I choose accessible colors from my brand palette?
Start with your brand colors as either foreground or background, then adjust the other color to achieve compliance. Use the lightness slider: if your brand color is dark, pair it with a light background; if it's light, pair with a dark/gray text. Alternatively, use slightly darker or lighter shades of your brand color that maintain brand identity while meeting contrast requirements.