The Web Content Accessibility Guidelines (WCAG) is a series of technical documents devised by the WAI Working Group to provide instructions on how to make the text, images and other elements that make up web content accessible to people with disabilities.
In May 1999, the WCAG Working Group published WCAG 1.0. The first version of WCAG provided technical guidelines based around a series of checkpoints with one of three priority levels. Anyone who applied the guidelines to their website and judged their site to conform to the checkpoints could claim that they had produced an accessible site.
Opportunities for refining and improving WCAG 1.0 became apparent as people set about implementing them. Meanwhile, the range of devices that accessed the web proliferated beyond the computer screen, greater bandwidth and storage space allowed for more sophisticated content and the way this content could be delivered evolved to using HTML5 and CSS3.
The Working Group set about making the guidelines broader based and able to be applied to a wider range of technologies and situations. Feedback told them WCAG also needed to be easier to read, understand and implement. By December 1998, the WCAG Working Group was ready to publish WCAG 2.0.
WCAG 2.0 introduced several improvements over WCAG 1.0, including:
- The adoption of four underpinning principles, that in order to be accessible web content should be:
- Criteria for determining whether content is accessible, and the means to test that according to three levels of conformance:
- Level A
- Level AA
- Level AAA
- The provision of supporting material for people implementing WCAG, including:
- a customisable quick reference
- articles that explained the context and application of the guidelines
- techniques for achieving conformance and examples of how to apply them
The format used for WCAG 2.0 follows that used by the W3C in all its guidelines, creating an interwoven and inter-related series of practical resources based on clear technical specifications. This attention to detail has resulted in WCAG 2.0 developing into a resource that runs to almost 200,000 words.