Meet minimum color contrast ratios

Rule Details

Text must have sufficient contrast against its background to ensure it is readable by as many people as possible, including those with low vision or color vision deficiencies.

Code Example

/* ✅ Good: Dark text on white — 21:1 ratio */
.body-text {
  color: #000000;
  background-color: #ffffff;
}
 
/* ✅ Good: #595959 on white meets 4.5:1 for normal text */
.secondary-text {
  color: #595959;
  background-color: #ffffff;
}
 
/* ✅ Good: #767676 on white meets 3:1 — only valid for large text (≥ 24px or ≥ 18.67px bold) */
.large-heading {
  font-size: 1.5rem; /* 24px at 16px base */
  font-weight: bold;
  color: #767676;
  background-color: #ffffff;
}
 
/* ❌ Fail: #cccccc on white is approximately 1.6:1 */
.placeholder-text {
  color: #cccccc;
  background-color: #ffffff;
}

Why It Matters

The thresholds in WCAG 1.4.3 Contrast (Minimum) (opens in new tab) and WCAG 1.4.11 Non-text Contrast (opens in new tab) are not aesthetic preferences; they are readability requirements for text and UI states people need to perceive.

• Low Vision: Users with moderately low vision (20/80 after correction) may not perceive text below 4.5:1 without assistive magnification.
• Color Blindness: Red-green color blindness affects ~8% of males — color alone cannot distinguish elements; contrast is the universal signal.
• Aging Vision: Contrast sensitivity decreases with age; older users benefit from higher contrast even without a clinical diagnosis.
• Environmental Factors: Bright sunlight washes out screens — higher contrast helps in outdoor use.
• Compliance: WCAG 2.1 Level AA (SC 1.4.3) is the baseline for most legal accessibility regulations (ADA, EN 301 549, AODA).

Contrast Ratio Requirements

Best Practices

• Check contrast in all interactive states: :hover, :focus, :active, :visited, and disabled.
• Disabled elements are technically exempt, but overly light disabled states still hurt usability.
• Use browser DevTools (Chrome/Firefox Accessibility panel) for quick checks during development.
• Do not rely solely on automated tools — manual checks with real content and backgrounds are needed.

Tools & Validation

• WebAIM Contrast Checker (opens in new tab)
• Colour Contrast Analyser (TPGi) (opens in new tab)
• WhoCanUse (opens in new tab) — simulates how different users perceive your colors

Exceptions

• Evaluate the rendered experience before treating a static-code smell as a blocker; interaction timing, browser behavior, and assistive technology output often determine severity.
• Not every secondary accessibility issue deserves equal weight; prioritize the issue that most directly blocks perception, operation, or understanding.
• Avoid adding redundant markup or ARIA solely to satisfy a rule when a simpler semantic implementation would eliminate the issue entirely.

Verification

Automated Checks

• Inspect the browser accessibility tree or accessibility pane for the relevant element, role, or accessible name.
• Run an automated accessibility checker such as axe or Lighthouse where applicable.

Manual Checks

• Test the affected UI with keyboard-only navigation and confirm the rule holds in the rendered experience.
• Re-test one representative user flow with a screen reader if this rule affects a key interaction.