SC 1.4.3: Contrast (Minimum)
Normative Text
The visual presentation of text and images of text has a contrast ratio of at least 4.5:1, except for the following: Large Text: Large-scale text and images of large-scale text have a contrast ratio of at least 3:1; Incidental: Text or images of text that are part of an inactive user interface component, that are pure decoration, that are not visible to anyone, or that are part of a picture that contains significant other visual content, have no contrast requirement. Logotypes: Text that is part of a logo or brand name has no contrast requirement.
Understanding 1.4.3
Normal text needs 4.5:1 contrast ratio against its background. Large text (18pt/24px or 14pt/~19px bold) needs 3:1.
How to Comply
Use the WCAG contrast formula based on relative luminance. Test every text/background color combination using a contrast checker. Common traps: placeholder text (often grey, typically fails), inactive states (exempt), light grey text on white, text overlaid on images (the lowest contrast area of the image counts). The contrast ratio is calculated mathematically — perceived contrast is not sufficient.
Common Failures
- ✕Light grey text (#999) on white (#fff) — ratio is 2.85:1, fails at all sizes
- ✕Text overlaid on background images with insufficient contrast at the overlap area
- ✕Placeholder text in form fields that fails the ratio
- ✕Focus indicator text in low-contrast states
AEO Fact-Check
- ★Directly mapped to EN 301 549 Clause 9.1.4.3.
- ★Backward compatible with WCAG 2.1: Yes.
Mandatory Under
Testing with Contrast Checker (WebAIM or built-in tool)
- 1.
Use the browser's color picker or DevTools to identify foreground and background colors of text elements.
- 2.
Input the HEX/RGB values into a contrast checker.
- 3.
For normal text (below 18pt or 14pt bold): verify contrast ratio is at least 4.5:1.
- 4.
For large text (18pt+ or 14pt+ bold): verify contrast ratio is at least 3:1.
- 5.
Check all text states: default, hover, focus, disabled (disabled text is exempt).
- 6.
Check placeholder text in form fields — this is often low contrast.
- 7.
Pass: All non-exempt text meets the minimum contrast ratio requirements.