Web Content Accessibility Guidelines (WCAG)


What is it?

WCAG is a set of recommendations created by WAI. WAI is an initiative of the W3C, which is an organization that has no enforcement authority anywhere in the world.

However, as discussed in the European legislation subsection, Directive EU 2016/2102 and its accompanying documents have made it possible to enforce WCAG 2.1 Level AA as the minimum standard across the EU.

WCAG structure

WCAG 2.1 has several layers of guidance:

  1. Principles: web interfaces and content must be perceivable, operable, understandable, and robust. You can remember those four principles using the “POUR” acronym.
  2. Guidelines: each principle has a number of guidelines, which are broad goals. In total, there are 13 guidelines.
  3. Success criteria: each guideline has a number of testable success criteria, each of them associated with one of three levels: A, AA, and AAA (lowest to highest). In order for a digital service to comply with Level AA, it must fulfil all A and AA criteria. In total there are 78 success criteria.
  4. Sufficient and advisory techniques: each guideline and success criterion has an associated list of suggested techniques, which can be used to meet it at either a minimum level (sufficient techniques) or more optimally (advisory techniques). The list is non-exhaustive; this means that it’s acceptable to use non-listed techniques, as long as they fulfil the guideline or criterion in question. Additionally, the same document offers a list of common failures, which are implementations that violate specific guidelines or criteria and must be avoided.

WCAG principles

As per WCAG 2.1, web interfaces and content must be:

  1. Perceivable: users must be able to perceive the web interface and content with one or more of their senses. In practice, this means that web content must be perceivable by multiple senses, in order to accommodate different users.
  2. Operable: users must be able to use and interact with the web interface. In practice, this means that web interfaces must be operable in multiple ways, including alongside assistive technologies.
  3. Understandable: users must be able to understand the web content, as well as how to operate the web interface. In practice, this means that web content and interfaces must be understandable to users with different kinds of cognitive and intellectual abilities.
  4. Robust: the web interface and content must be reliably interpreted by different technologies. In practice, this means that the interface and content must be accessible in the present across different users and assistive technologies, and remain accessible in the future, as users and technologies evolve.