Web Content Accessibility Guidelines (WCAG)

About the Web Content Accessibility Guidelines

The Web Content Accessibility Guidelines (WCAG) are the most popular digital accessibility standards.

WCAG outlines the requirements that most consultants and subject matter experts use to test for digital accessibility. It is also specified as the official requirement under certain laws, like Section 508 of the Rehabilitation Act, and it is commonly pointed to in digital accessibility lawsuits and complaints.

The World Wide Web Consortium (W3C) Web Accessibility Initiative (WAI) publishes and maintains WCAG.

The first version of WCAG was published in 1999. The latest version, WCAG 2.1, was published in 2018.

WCAG structure

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.

Example of WCAG breakdown

Success Criterion 1.4.1 Use of Color states: "Color is not used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element."

This Success Criterion is one of the Success Criteria under Guideline 1.4 Distinguishable, which states: "Make it easier for users to see and hear content including separating foreground from background."

This Guideline is one of the Guidelines under Principle 1. Perceivable, which states: "Information and user interface components must be presentable to users in ways they can perceive."

WCAG conformance levels

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

Level AA conformance of WCAG 2.0 or 2.1 is most common.

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.

To achieve Level AA conformance therefore means to satisfy all Level A and AA Success Criteria. "It is not recommended that Level AAA conformance be required as a general policy for entire sites because it is not possible to satisfy all Level AAA Success Criteria for some content," according to W3C's Understanding Conformance.

Understanding what WCAG conformance means

To claim compliance or conformance with WCAG requires understanding what constitutes conformance. W3C's Understanding Conformance explains: "Conformance to a standard means that you meet or satisfy the 'requirements' of the standard. In WCAG 2.0 the 'requirements' are the Success Criteria. To conform to WCAG 2.0, you need to satisfy the Success Criteria, that is, there is no content which violates the Success Criteria."

There are five requirements for conformance, per W3C:

  1. Conformance level: One of the following levels of conformance is met in full (Level A, Level AA, Level AAA, or a conforming alternate version is provided).
  2. Full pages: Conformance (and conformance level) is for for Web page(s) only, and cannot be achieved if part of a Web page is excluded.
  3. Complete process: When a Web page is one of a series of Web pages presenting a process (i.e., a sequence of steps that need to be completed in order to accomplish an activity), all Web pages in the process conform at the specified level or better. (Conformance is not possible at a particular level if any page in the process does not conform at that level or better.)
  4. Only Accessibility-Supported Ways of Using Technologies: Only accessibility-supported ways of using technologies are relied upon to satisfy the success criteria. Any information or functionality that is provided in a way that is not accessibility supported is also available in a way that is accessibility supported.
  5. Non-interference: If technologies are used in a way that is not accessibility supported, or if they are used in a non-conforming way, then they do not block the ability of users to access the rest of the page (as well as additional requirements).

For more information, review W3C's Understanding Conformance.

Helpful WCAG resources