Color Contrast Checker
The Color Contrast Checker evaluates whether the contrast ratio between text and background colors meets WCAG (Web Content Accessibility Guidelines) standards, helping designers and developers create interfaces with better visual accessibility.
What is Color Contrast
Color contrast refers to the degree of light-dark difference between foreground colors (such as text) and background colors, expressed numerically, ranging from 1:1 (no contrast) to 21:1 (maximum contrast, such as black and white).
Good color contrast ensures content is readable for all users, including those with visual impairments, color blindness, and users viewing devices in bright or dim lighting conditions.
WCAG Standards
WCAG defines two levels of contrast ratio standards:
AA Level Standard (Minimum Requirement)
- Normal Text: Contrast ratio of at least 4.5:1
- Large Text: Contrast ratio of at least 3:1
- Graphical Components: Contrast ratio of at least 3:1
AAA Level Standard (Enhanced Requirement)
- Normal Text: Contrast ratio of at least 7:1
- Large Text: Contrast ratio of at least 4.5:1
- Graphical Components: Contrast ratio of at least 4.5:1
Large Text Definition: Font size of at least 18pt (approximately 24px), or bold and font size of at least 14pt (approximately 18.5px).
Key Features
The tool supports real-time calculation of contrast ratio between text color and background color, providing AA and AAA level compliance checks. Visual display of actual effects for normal text, large text, and graphical components makes readability assessment intuitive.
Supports brightness adjustment, using sliders to quickly optimize contrast ratio without manually trying multiple color values.
Usage Instructions
- Select WCAG level (AA or AAA)
- Enter or select text color
- Enter or select background color
- View contrast ratio value and compliance results
- Adjust colors based on actual effect preview
- Use brightness slider to quickly optimize contrast ratio
Parameter Descriptions
WCAG Level: Choose AA level (standard requirement) or AAA level (enhanced requirement). Most websites and applications need to meet AA level standards; AAA level is suitable for scenarios with higher accessibility requirements.
Text Color: Foreground color, typically the color of text, icons, buttons. Supports manual input of hexadecimal color values or use of color picker.
Background Color: Background color, typically the color of pages, cards, containers. Supports manual input or use of color picker.
Brightness Adjustment: Adjust the brightness (lightness) of text or background color through slider, maintaining hue and saturation constant, to quickly optimize contrast ratio.
Calculation Results Explained
Contrast Ratio Value
Displays the contrast ratio between text color and background color, such as 4.5:1, 7.2:1, etc. The larger the value, the higher the contrast and the better the readability.
Compliance Check
The tool checks whether normal text, large text, and graphical components pass standards based on the selected WCAG level, intuitively displaying results with icons and colors (green for pass, red for fail).
Actual Effect Preview
Displays previews for three actual application scenarios:
- Normal Text: Simulates the effect of normal font size text
- Large Text: Simulates the effect of large font size text
- Graphical Components: Simulates the effect of graphical elements like icons and buttons
Application Scenarios
Web Design
When designing website color schemes, check the contrast ratio between text and background to ensure compliance with accessibility standards and enhance user experience.
Mobile App Development
When designing mobile app interfaces, verify the readability of buttons, labels, prompt text, and other elements to adapt to different lighting environments.
Brand Design
When establishing brand visual specifications, ensure that brand color and text combinations meet contrast standards to maintain readability in various application scenarios.
Accessibility Audit
During accessibility audits, quickly check the contrast ratio of all text elements in the interface to identify and fix non-compliant color combinations.
Presentations
When designing PPT, posters, and promotional materials, ensure text is clearly readable against backgrounds.
Usage Recommendations
Prioritize Meeting AA Level Standards
Unless there are special accessibility requirements, generally meeting AA level standards is sufficient. AAA level standards have higher requirements and may limit design flexibility.
Use Brightness Adjustment for Quick Optimization
If color contrast is insufficient, using the brightness slider to adjust text color or background color lightness is typically more efficient than manually trying multiple color values.
Pay Attention to Actual Effects
In addition to numerical values, view actual effect previews to ensure good readability in real scenarios. Some color combinations may pass contrast standards but still lack visual clarity.
Consider Color Blindness
Color contrast checking mainly addresses light-dark contrast issues but cannot completely solve readability problems for color-blind users. It's recommended to avoid relying solely on color to convey information, combining with icons, text labels, etc.
Choices for Different Scenarios
- Body Content: Recommend meeting AAA level normal text standard (7:1)
- Navigation, Buttons, Links: Recommend meeting AA level normal text standard (4.5:1)
- Headings, Large Text: Can use AA level large text standard (3:1)
- Decorative Text: No mandatory requirements, but still recommend maintaining certain contrast
Important Notes
WCAG standards primarily target text content; purely decorative elements (such as background patterns) have no mandatory contrast requirements.
Contrast calculation is based on relative luminance and generally aligns with human perception of color differences, but deviations may exist in some special color combinations.
The tool checks static color contrast; practical applications must also consider the effects of animations, gradients, transparency, and other factors.
Meeting contrast standards is an important part of accessibility design but not all of it. Complete accessibility design also includes keyboard navigation, screen reader support, focus management, and other aspects.
Common Questions
Why does my design pass contrast checking but still look unclear$1
Contrast calculation is based on relative luminance; some color combinations (such as red-green, blue-yellow), while having sufficient luminance contrast, may have indistinct hue differences and appear visually unclear. It's recommended to combine with actual effect preview adjustments.
Why are standards different for large text and normal text$2
Large text, due to its larger font size and thicker strokes, can maintain readability even with slightly lower contrast, so standards are relatively more lenient.
What are the contrast requirements for graphical components$3
Graphical components (such as icons, button borders, chart elements) must have a contrast ratio with adjacent colors of at least 3:1 (AA level) or 4.5:1 (AAA level).
Can I only adjust text color without changing background color$4
Yes. The tool supports adjusting the brightness of text color or background color independently. Choose which to adjust based on actual design needs.
Some websites use gray text, does this meet standards$5
Light gray text on white backgrounds may not meet contrast standards. It's recommended to use the tool to check specific values; if non-compliant, deepen text color or adjust background color.
Is higher contrast always better$6
Not necessarily. Excessively high contrast (such as pure black and white) may cause eye fatigue. It's recommended to choose visually comfortable color combinations while meeting standards.
