What's The Difference Between WCAG Level A, Level AA, and Level AAA?

December 17, 2021

In order to embrace web accessibility as a priority, you need to set goals and track your progress. The Web Content Accessibility Guidelines (WCAG) provide the best available framework; published by the World Wide Web Consortium (W3C), WCAG is the consensus standard for digital accessibility. 

WCAG is based on four main principles: Content must be perceivable, operable, understandable, and robust. The guidelines — also called success criteria — provide actionable information for creating better websites and mobile applications. To provide an organized structure, the guidelines are classified into three conformance levels: 

  • Level A - Considered the least strict, Level A success criteria are essential for every website. If your website doesn’t conform with WCAG Level A, it may have serious accessibility issues that prevent users with disabilities from using it. 
  • Level AA - Websites that conform with WCAG Level AA can be considered reasonably accessible for most users. Most websites should aim for Level AA conformance. To meet this goal, content must conform with all Level AA and Level A success criteria.
  • Level AAA - Digital content that conforms with WCAG Level AAA is considered optimally accessible. To earn Level AAA conformance, content must pass every guideline in WCAG (including Level AA and Level A success criteria).  However, some Level AAA success criteria are extremely strict, and some types of content cannot conform with every guideline at this level. 

As mentioned above, most websites should try to earn Level AA conformance with the latest version of WCAG (currently, the latest version is WCAG 2.1, but WCAG 2.2 may be released in the upcoming months. Read our article about the differences between WCAG 2.1 and WCAG 2.2 for more information). 

WCAG Level AA conformance demonstrates reasonable accessibility

If a website fails to conform with WCAG 2.1 Level A success criteria, it has serious accessibility barriers. Level A success criteria requires text alternatives for non-text content, keyboard navigability, and other basic considerations. 

However, the goal of digital accessibility is to make content useful for your entire audience — Level A conformance is an excellent starting point, but Level AA goes further by ensuring that your content is practically useful for most people, regardless of their abilities. Many accessibility laws require Level AA conformance for this reason.

Some examples of Level AA success criteria: 

WCAG 2.1 Success Criterion 1.4.3, “Contrast Levels (Minimum)” 

Color contrast is the difference in light between foreground elements (including text) and the background. WCAG Level AA requires a contrast ratio of at least 4.5:1 for normal text; large text should have a contrast ratio of at least 3:1. 

Related: The Basics and Importance of Color Contrast for Web Accessibility

WCAG 2.1 Success Criterion 2.4.6, “Headings and Labels"  

Your content includes descriptive headings, which can help people who have trouble reading or who navigate via keyboard. Headings provide structure to your content, which improves readability and helps with search engine optimization.

Related: What Are H Tags? How Headings Affect User Experience

WCAG 2.1 Success Criterion 1.3.4, “Orientation”

To pass this guideline, your content shouldn’t restrict its view and operation to a single display orientation. For example, if a user accesses your website on a mobile device, they shouldn’t lose access to information or functionality if they choose to view the website in portrait or landscape mode.

Related: Improve Mobile Website and App Accessibility

Unfortunately, the vast majority of websites don’t conform with WCAG Level AA. Each year, non-profit organization WebAIM performs automated evaluations of the home pages of the top one million websites. In WebAIM’s 2021 report, 97.4% of home pages failed to comply with WCAG Level AA.

Many WCAG Level AAA guidelines can improve your content

If you’re starting an accessibility initiative, WCAG 2.1 Level AA conformance is a reasonable goal. By following the guidelines, you can enjoy improved search engine optimization, higher user retention rates, and the other benefits of digital accessibility.

However, you shouldn’t ignore WCAG’s Level AAA guidelines. While these success criteria are strict, they provide additional guidance for expanding your audience. For example, Level AAA guidelines require a color contrast ratio of at least 7:1 in most instances; some sites can conform with this guideline easily, and by doing so, they can provide a better experience for more of their users.

To meet your accessibility goals, you’ll need to identify current WCAG conformance failures, then track your progress as your website improves. The Bureau of Internet Accessibility offers WCAG 2.1 A/AA accessibility audits, which combine artificial intelligence with manual testing to provide accurate information and recommendations.

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