Text contrast accessibility

Viktoria Vass

What is color contrast?

Color contrast refers to the difference in brightness and color between text and its background. High contrast makes text easy to read, while low contrast can make it difficult or impossible for some learners to see.

Providing sufficient contrast is an essential accessibility practice. It ensures that all learners, regardless of vision ability, can read and understand your content.

For example:

• Black text on a white background = high contrast
• Light gray text on a white background = low contrast

High contrast makes content readable for most users, while low contrast can create strain or make text invisible for learners with certain visual impairments.

WCAG AA contrast requirements specify:

• 4.5:1 minimum contrast ratio for normal (small) text.
• 3:1 minimum contrast ratio for large text.

“Large text” is defined as text that is at least 18pt or text that is at least 14pt and bold.

Affected learners

Learners with low vision

Learners with reduced visual acuity may struggle to read text if there isn’t enough contrast. Even slight differences in brightness can make letters blur together or disappear.

Learners with color vision deficiencies

Red-green color blindness, which is the most common form of color blindness, and other color vision deficiencies can make certain text-background combinations unreadable.

Learners using small screens or poor lighting

Even learners without visual impairments can struggle with low-contrast text when using small devices, mobile screens, or working in bright or dim environments.

Learners using assistive technologies

Some assistive technologies rely on contrast to highlight content or enhance readability. Low contrast reduces their effectiveness.

Why contrast matters

Good contrast is about more than readability and ensuring equal access to information. Low-contrast text can:

• Slow reading speed: learners must strain or reread
• Increase fatigue: extended reading becomes tiring
• Cause missed information: learners may miss critical instructions or content
• Exclude learners: learners with visual impairments may be unable to access key material at all