WCAG 2.0 (Web Content Accessibility Guidelines)
The Web Content Accessibility Guidelines (WCAG) 2.0 are the internationally accepted standard for the accessibility of web content. WCAG 2.0 also serve as a bluebrint for many national regulations and directives.
Some countries reference WCAG 2.0 straight away, others have opted to develop their own regulations which are often based on WCAG 2.0, at times adding further requirements. For example, the German BITV 2.0 (Barrierefreie Informationstechnik-Verordnung) mainly follows WCAG 2.0 but mandates versions in simple language and sign language for the start pages of federal institutions.
WCAG principles, guidelines, and success criteria
The requirements of WCAG 2.0 are hierarchically ordered in 4 principles (perceivable, operable, understandable and robust), 12 guidelines, and 62 success criteria.
The three conformance levels of WCAG
WCAG requirements are layered in three different conformance levels. Level A includes basic success criteria, level AA adds further criteria that cover things like text scalability and contrast, and level AAA includes a number of additional often quite demanding success criteria, such as sign language versions.
- Level A: These are the basic criteria that must be met by web content in any case, such as full keyboard operability, alternative text for graphics carrying information, captions for video with language, and the semantic mark-up of content. For example, form fields need a label, and visually distinct headings must also be marked up as headings for blind users.
- Level AA: On this level, a number of important success criteria are added, such as the visibility of keyboard focus, good text contrast, and good scalability of content. Many success criteria on this level are particularly important for low vision users.
- Level AAA. This level adds further success criteria, such as the provision of content versions in sign language, the use of easy-to-read text, full transcriptions of videos, and stronger contrasts and a single column view for text. WCAG do not recommend level AAA as a generally applicable conformance level, since for many types of content it is difficult to meet all of its success criteria (compare 'Understanding Conformance Requirements', Understanding Requirement 1, Note 2).
In addition to the normative text of WCAG 2.0 there are a great number of informal WCAG techniques that demonstrate accessible implementations. Whether or not a particular WCAG technique has been implemented correctly should be determinable according to the tests that are present at the end of most techniques. In addition, a number of Common Failures have been documented.
The principle of conformance
WCAG 2.0 aims to afford a conformance test of web content.
The conformance of a page to one of the three conformance levels (A, AA, AAA) can be established by testing its web content against all success criteria on the selected level and levels below. This means that conformance on level AA means that a page meets all success criteria on level A and on level AA.
In each case, all five conformance requirements must be met in addition to meeting the success criteria. For example, conformance must be established for entire pages and complete processes (even if these span several pages).
Methods for testing against WCAG
Currenty the WCAG Evaluation Methodologies Task Force of W3C is developing a harmonised methodology that is intended to provide the basis for a conformance-oriented evaluation of web sites and applications based on WCAG 2.0. The Website Accessibility Conformance Evaluation Methodology (WCAG-EM) 1.0 currently exists as a working draft.
WCAG also for non-web content?
The requirements for accessible web content that have been developed in WCAG can to a good part be transferred to other applications and types of content that are not web-based. However, there are alos differences: often applications do not follow a page model.
A task force of WCAG Working Group has produced a Working Group Note with recommendations as to the applicatino of WCAG to non-web content: Guidance on Applying WCAG 2.0 to Non-Web Information and Communications Technologies (WCAG2ICT).
This document has not yet been translated into German.