Note: The creation of this article on testing Contrast (Enhanced) was human-based, with the assistance on artificial intelligence.
Explanation of the success criteria
WCAG 1.4.6 Contrast (Enhanced) is a Level AAA conformance level Success Criterion. It ensures that text and images of text have a contrast ratio of at least 7:1 for normal text and 4.5:1 for large text.
WCAG 1.4.3 Contrast (Minimum) and WCAG 1.4.6 Contrast (Enhanced) both address the visibility of text by setting minimum contrast ratios between text and its background. The key difference lies in their strictness and conformance levels:
- 1.4.3 requires a contrast ratio of at least 4.5:1 for normal text and 3:1 for large text, making it a Level AA requirement aimed at basic readability.
- 1.4.6 raises the bar with a higher minimum contrast ratio of 7:1 for normal text and 4.5:1 for large text, designated as Level AAA, to support users with more severe visual impairments.
Essentially, 1.4.6 builds on 1.4.3 by demanding stronger contrast to enhance accessibility for those who need it most.
If you wish to get more information on the details and minutia of this success criterion, check out the Understanding documentation.
Note that this Success Criterion is at a conformance level of AAA. This means that this Success Criterion is generally considered aspirational, going beyond the standard A & AA conformance levels. It addresses more specific accessibility needs and is not mandatory for all websites or content. However, achieving Level AAA can provide additional benefits in terms of inclusivity.
Who does this benefit?
- People with low vision often struggle to read text that lacks strong contrast against its background, especially if they also have color vision deficiencies that further reduce contrast.
- Rare individuals who see no color at all.
Testing enhanced contrast via Automated testing
Automated testing is fast and efficient, quickly scanning large amounts of text and images to flag contrast issues that fail the 7:1 or 4.5:1 ratios. It helps catch widespread problems early in development.
However, these tools can miss text on images, gradients, or dynamic backgrounds and often struggle to correctly judge font size or weight. They may also misidentify what counts as text.
Testing enhanced contrast via Artificial Intelligence (AI)
AI-based testing offers strong advantages for evaluating contrast, especially on dynamic or visually complex pages. It can scan entire interfaces, simulate color vision deficiencies, and provide a more user-centered view than basic contrast checkers. This makes it especially helpful for identifying issues traditional tools might miss.
However, AI tools aren’t foolproof. They can misinterpret contrast where text appears over gradients, images, or custom components, and may either flag compliant designs or miss subtle failures. Since WCAG 1.4.6 requires stricter contrast thresholds, AI tools may need careful tuning.
Testing enhanced contrast via Manual testing
Manual testing brings valuable human judgment to contrast evaluations, especially in complex visuals like gradients, images, or patterned backgrounds that automated tools may misread. It also helps confirm whether text qualifies as “large,” which can vary with styling.
However, it’s time-consuming, less precise without contrast tools, and prone to inconsistencies or missed issues on content-heavy pages.
Which approach is best?
No single approach for testing 1.4.6 Contrast (Enhanced) is perfect. However, using the strengths of each approach in combination can have a positive effect.
The most effective way to test this success criterion is by combining automated, AI-based, and manual methods. Automated tools quickly flag low-contrast text, AI tools catch issues in complex layouts and backgrounds, and manual testing ensures readability over patterns and corrects text size classification. Together, they deliver thorough, reliable results.