WCAG 1.4.3 Contrast (Minimum)

[wcgadmfrm]

Understanding WCAG 1.4.3: Contrast (Minimum)

Hi everyone!

Today we explore a crucial WCAG criterion for readability and visual perception: WCAG 1.4.3 Contrast (Minimum). This is a Level AA criterion, meaning it's a common and important requirement for most websites.

What is WCAG Success Criterion 1.4.3?

This criterion states that:
"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 (at least 18pt regular or 14pt bold) has a contrast ratio of at least 3:1.
• Incidental: Text that is part of an inactive user interface component, that is pure decoration, or that is not visible to anyone, or that is part of a picture that contains significant other visual content, has no contrast requirement.
• Logotypes: Text that is part of a logo or brand name has no contrast requirement.

In practice, it's about ensuring there's enough difference in luminosity between the text and its background, making it readable for a wide range of users.

Why is Good Contrast Crucial?

Adequate contrast is vital for:

• Users with Low Vision: Many people with visual impairments (but not blindness) benefit greatly from high contrast.
• Aging Users: Eyesight tends to deteriorate with age, and good contrast aids readability.
• Individuals with Cognitive Disabilities or Learning Difficulties: Clear text reduces cognitive effort.
• Adverse Environmental Conditions: Glossy screens, direct sunlight, or dim lighting can make low-contrast text unreadable for anyone.

How to Measure Contrast? Ratios and Tools:

The contrast ratio is measured with a specific formula that considers the relative luminosity of colors.

• Normal Text: Minimum 4.5:1
• Large Text: Minimum 3:1 (large text is defined as at least 18pt or 14pt and bold)

Numerous online tools and browser plugins exist to check contrast ratios. Some popular ones include:

• WebAIM Contrast Checker
• Color Contrast Analyzer (browser extension)
• Built-in browser inspection tools (e.g., Chrome DevTools, Firefox Developer Tools)

Examples of Contrast (Imagine the colors):

• Good Contrast (e.g., black on white): Very high contrast ratio (> 7:1), excellent readability.
• Sufficient Contrast (e.g., dark blue on light gray): Contrast ratio 4.5:1 (or 3:1 for large text), readability guaranteed per WCAG.
• Low Contrast (e.g., light gray on white or light blue on white): Insufficient contrast ratio (< 4.5:1), difficult for many users to read.

Let's Discuss:

What are the biggest challenges you face in balancing visual design with contrast requirements? Do you have preferred tools for contrast checking? What are the most common contrast errors you see?

Warm regards,

Michele (wcgadmfrm)
WCAG Plus Forum Team