WebAIM - Web Accessibility In Mind

Web Content Accessibility Guidelines


A WCAG 2.0 Checklist is available for developers to use in implementing and verifying conformance with WCAG 2.0.

The W3C's Web Accessibility Initiative

Web Accessibility Initiative logo The W3C is an international, vendor-neutral group that determines the protocols and standards for the web. They create the specifications for HTML, CSS, etc. A primary initiative of the W3C is to develop accessibility standards. The goal of the Web Accessibility Initiative (WAI) is to develop these accessibility standards. WAI working groups develop accessibility standards for web browsers, authoring tools, evaluation tools, and web content, to name a few. The Web Content Work Group's standards are called the Web Content Accessibility Guidelines (WCAG).

WCAG 1.0

Version 1.0 of the Web Content Accessibility Guidelines was a major development in making the Internet more accessible to people with disabilities. Finalized in 1999, WCAG 1.0 provided 14 guidelines and numerous checkpoints that could be used to determine the accessibility of a web page. It provided 3 priorities or levels of conformance (the measure to which a web page follows the guidelines). Priority 1 or Level A conformance was a basic requirement for some groups to be able to use web documents. Priority 2 or Level AA conformance indicated better accessibility and removal of significant barriers to accessing the content. Priority 3 or Level AAA checkpoints provided improvements to web content accessibility. WCAG 1.0 was very HTML specific. It was also the primary resource from which the Section 508 guidelines were drawn.

Over time, WCAG 1.0 began to show its age. As web technologies and technologies for people with disabilities advanced, conformance became more difficult as some checkpoints became less relevant and more difficult to verify. Thus the development of WCAG 2.0 began.

WCAG 2.0

The Web Content Accessibility Guidelines 2.0 builds upon the foundation of WCAG 1.0, but also introduces some significant changes worth discussing. On a practical level, some of the changes in WCAG 2.0 are subtle. For example, forms still require labels, data tables still require headers, and images still require alternative text. Web developers who currently design accessible web sites will not have to change their habits much. On the other hand, WCAG 2.0 represents a substantial shift in philosophy. The significant changes involve making the guidelines principle-centered rather than technique-centered. This allows the guidelines to be relevent even as technology changes. Additionally, they are designed so that conformance can be reliably verified. While measuring true conformance can be difficult, the guidelines are structured to allow less interpretation of what true conformance means.

The shift from technique-centered guidelines to principle-centered guidelines resulted in a reduced number of top level ideas, or principles. WCAG 1.0 had fourteen principles at the top level. WCAG 2.0 places only four principles at the top level under which more specific guidelines, called success criteria, are organized. These four principles can each be referred to by a single keyword:

  • Perceivable
  • Operable
  • Understandable
  • Robust

These principles are discussed in depth in Constructing a POUR Website.