Color Contrast
Problem
- Users in general, and particularly those with low vision, have trouble reading text if the contrast against the background is insufficient.
Examples
Good Contrast |
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All the things one has forgotten scream for help in dreams - Elias Canetti |
All the things one has forgotten scream for help in dreams - Elias Canetti |
Poor Contrast |
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All the things one has forgotten scream for help in dreams - Elias Canetti |
All the things one has forgotten scream for help in dreams - Elias Canetti |
WCAG Success Criteria
WCAG Sufficient Techniques
- Text less than 18 point if not bold and less than 14 point if bold
G18: Ensuring that a contrast ratio of at least 4.5:1 exists between text (and images of text) and background behind the text - Text at least 18 point if not bold and at least 14 point if bold
G145: Ensuring that a contrast ratio of at least 3:1 exists between text (and images of text) and background behind the text
Testing Method
- Install the WCAG Color Checker toolbar for Firefox
- Open Firefox
- Click on Tools > ColorChecker
- The Color Checker panel will open
- Click on 'Document' and then 'Test (WCAG 2)'
- Is the Luminosity Ratio above 4.5 for all text elements? (Tip: You can click on each ratio to see what text it refers to)
- Tip: For additional testing try Contrast Analyzer
Exercise
Tip
- It is much easier to achieve sufficient contrast by using dark text on a light background.