AA vs AAA Compliance

AA and AAA represent two conformance levels within WCAG accessibility standards, with AAA imposing stricter requirements than AA. Understanding the differences between these levels helps design system teams set appropriate accessibility targets and communicate compliance expectations clearly.

What Are AA and AAA Compliance Levels

WCAG organizes success criteria into three conformance levels: A, AA, and AAA. Level A addresses the most basic accessibility requirements. Level AA builds on Level A with additional criteria that address broader accessibility needs. Level AAA includes all A and AA criteria plus the most stringent requirements.

Level AA has become the standard compliance target for most organizations, legal frameworks, and industry guidelines. The Americans with Disabilities Act, European Accessibility Act, and Section 508 generally align with AA requirements. Level AAA compliance, while beneficial, presents practical challenges and is not typically mandated.

The distinction matters for design systems because the target level determines specific requirements for color contrast, text sizing, timing functions, and other component characteristics.

How AA and AAA Requirements Differ

Color contrast requirements represent the most visible difference. AA requires 4.5:1 contrast for normal text and 3:1 for large text. AAA increases these to 7:1 and 4.5:1 respectively. This stricter requirement significantly constrains which color combinations remain usable, potentially limiting brand expression.

Text size and spacing criteria also differ. AAA requires that text can be resized up to 200% without loss of content or functionality (also required at AA) but adds requirements for line height, paragraph spacing, and letter spacing that exceed AA standards.

Timing requirements become more restrictive at AAA. While AA allows some time limits with extension options, AAA prohibits timing in more contexts. Auto-updating content requires pause mechanisms. Interruptions must be suppressible.

Navigation assistance criteria expand at AAA. Beyond the basic skip links and heading structure required at AA, AAA adds requirements for section headings, multiple navigation mechanisms, and more detailed link purpose descriptions.

AAA also includes criteria around sign language for audio, extended audio description for video, and simpler reading levels that few design systems can directly address through components alone.

Key Considerations

• AA compliance serves as the baseline target for most design systems
• AAA contrast ratios (7:1 for text) may conflict with brand color guidelines
• Some AAA criteria apply to content rather than components (reading level, sign language)
• Design systems can exceed AA in specific areas without claiming full AAA compliance
• Legal requirements typically reference AA, making it the practical minimum
• Document which compliance level the design system targets and any areas of elevated compliance
• Consider offering AA-compliant defaults with AAA-compliant alternatives for enhanced accessibility

Common Questions

Should design systems target AA or AAA compliance?

Most design systems should target AA compliance as a baseline, with AAA as a stretch goal for specific criteria where achievable. Full AAA compliance is rarely practical because some criteria conflict with common design patterns or require content-level decisions beyond component scope.

A pragmatic approach identifies AAA criteria achievable without significant tradeoffs and implements those while clearly meeting all AA requirements. For example, a design system might achieve AAA contrast ratios for critical UI elements while maintaining AA for less prominent text.

Can design systems claim AAA compliance?

Claiming full AAA compliance requires meeting every AAA criterion across all content. Since some AAA criteria depend on content rather than components (reading level, sign language translation), component libraries alone cannot achieve this.

Design systems can accurately claim AA compliance for their components and note specific areas where AAA criteria are met. Documentation should be precise about compliance claims rather than implying broader compliance than achieved.

How do compliance levels affect design system adoption?

Organizations in regulated industries or government contexts often require specific compliance levels. A design system that clearly documents its AA compliance becomes easier to adopt for these organizations because compliance evidence already exists.

Teams may also have internal accessibility mandates that reference WCAG levels. Design systems that meet or exceed these mandates reduce the compliance burden on consuming teams, encouraging adoption.

Summary

AA and AAA represent escalating WCAG compliance levels, with AA serving as the standard target for most design systems and legal frameworks. AAA provides stricter requirements, particularly around color contrast and timing, that may prove impractical for full compliance but can guide enhanced accessibility in specific areas.