On this page
  1. How do we understand and implement accessibility?
  2. What is Web Accessibility Initiative?
  3. WCAG Guidelines and Success Criteria
  4. WCAG conformance levels
  5. Summary
  6. Minimum requirements
  7. Final notes

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What is digital accessibility?

Learn what's digital accessibility and how that impacts site usage.

Digital accessibility refers to providing an equivalent user experience for people with disabilities, including auditory, cognitive, neurological, physical, speech, and visual disabilities. That means also providing web-based information, digital content, applications, and resources that are available and used by everyone.

Making a website accessible can be simple or complex, depending on many factors such as the type of content, the size, technology, complexity of the site, the development tools, and the environment.

Many accessibility features are easily implemented if they are planned and developed from the beginning of development or redesign. Fixing inaccessible sites may require significant effort, especially sites that were not originally coded properly with standard HTML markup, and sites with certain types of content such as multimedia.

How do we understand and implement accessibility?

We know now what’s digital accessibility, but we don’t know how to implement it. Web Accessibility Initiative to the rescue. One of the roles of the Web Accessibility Initiative (WAI) is to develop guidelines and techniques that describe accessibility solutions for web software and developers. These WAI guidelines are considered the international standard for Web accessibility.

What is Web Accessibility Initiative?

The Web Accessibility Initiative (WAI) guidelines are widely regarded as the international standard for web accessibility. WAI provides resources on its website and works by developing support materials to help understand and implement web accessibility and developing resources, through international collaboration.

Part of the Web Accessibility Initiative is Web Content Accessibility Guidelines (WCAG) that are part of a series of web accessibility guidelines.

In 2008, the World Wide Web Consortium (W3C) published the Web Content Accessibility Guidelines (WCAG; pronounced: way-cagg or wuh-cog) to specify how web developers should make content accessible for people with disabilities. The WCAG 2.0 and higher have Success Criteria split between three Levels of Conformance (low to high): A, AA, and AAA, with AAA being the level that makes your content the most accessible.

The latest version of WCAG is 3.0 and it’s marked as Working Draft of WCAG 3.0.

WCAG Guidelines and Success Criteria

WCAG is organized by four Principles, which state that content must be Perceivable, Operable, Understandable, and Robust. The four Principles are arranged by supporting Guidelines, which are further broken into individual Success Criteria. Success Criteria act as the specific and testable accessibility requirements.

There are 13 guidelines in WCAG 2.1 containing a total of 78 success criteria, that represent basic goals web authors and developers should aim for. Guidelines provide a framework for organizing success criteria.

WCAG conformance levels

There are three conformance levels of WCAG: Level A, Level AA, and Level AAA.

Each Success Criterion is assigned a conformance level of A, AA, or AAA, with A as the lowest level of compliance and AAA as the highest. To qualify as meeting a certain conformance level, all content on a webpage or website must fully meet at least that level.


Summary of WCAG Success Criteria and Conformance Level
Success Criteria
LevelDescriptionWCAG 2.0WCAG 2.1Total WCAG
2.0 and 2.1
ALevel A success requirements are the least strict. If your digital content does not meet WCAG Level A, it may have major accessibility concerns that prevent disabled visitors from using it.25530
AADigital content that conforms 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.17720
AAADigital content that meets WCAG Level AAA is considered best accessible. To achieve Level AAA conformity, content must meet all of the WCAG guidelines (including Level AA and Level A success criteria). Some Level AAA success criteria, however, are quite strict, and some types of content cannot adhere to every criterion at this level.23528

Minimum requirements

The general recommendation is to comply with WCAG 2.1. Level AA standard for accessibility to ensure that content and functionality are Perceivable, Operable, Understandable, and Robust for those affected by:

  • Visual impairment and blindness.
  • Hearing impairment and deafness.
  • Physical disabilities such as congenital conditions, long-term injuries caused by accidents Neurological conditions, and brain injuries.
  • Speech and language disabilities.
  • Learning disabilities or differences.

Additionally, persons without disabilities will gain from it:

  • People using smart watches, smart TVs, mobile phones, and other devices with small screens, different input modes, etc. Older people with changing abilities due to aging.
  • Those who have temporary disabilities, like a broken arm or lost glasses.
  • People who have situational limitations, such as those who cannot hear sounds in environments, with bright sunlight or high sunlight, those with a slow Internet connection, or with expensive or limited bandwidth.

Final notes

Quote from W3C:

When citing WCAG 2.1 as part of a requirement (e.g., a shall or must statement in a standard or regulation), the reference must include the specific parts of WCAG 2.1 that are intended to be required. When referencing WCAG 2.1 in this manner, the following rules apply:

  1. Conformance at any level of WCAG 2.1 requires that all of the Level A Success Criteria be met. References to WCAG 2.1 conformance cannot be for any subset of Level A.
  2. Beyond Level A, a shall or must reference may include any subset of provisions in Levels AA and AAA. For example, all of Level A and [some specific list of Success Criteria in Level AA and Level AAA] be met.
  3. If Level AA conformance to WCAG 2.1 is specified, then all Level A and all Level AA Success Criteria must be met.
  4. If Level AAA conformance to WCAG 2.1 is specified, then all Level A, all Level AA, and all Level AAA Success Criteria must be met.

    Note 1: It is not recommended that Level AAA conformance ever be required for entire sites as a general policy because it is not possible to satisfy all Level AAA Success Criteria for some content.

    Note 2: The sets of Success Criteria defined in WCAG are interdependent and individual Success Criteria rely on each other’s definitions in ways which may not be immediately obvious to the reader. Any set of Success Criteria must include all of the Level A provisions.

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