Made available by the International Digital Publishing Forum (IDPF) (now merged with the World Wide Web Consortium (W3C)), EPUB accessibility establishes several guidelines to allow the evaluation and certification of accessible EPUB Publications, as well as enabling the discovery of the accessible qualities of EPUB Publications.
EPUB accessibility takes the same approach used by Web Content Accessibility Guidelines (WCAG): it establishes principles and guidelines that are abstract, yet practical enough to be implemented with any available technology. A more technical document (EPUB Accessibility Techniques 1.1) provides detailed, technology agnostic guidance on how to meet these guidelines.
According to the specification, EPUB publications accessibility can be classified in three different levels:
- discoverable: the publication meet the specification requirements about the metadata to allow the discovery of accessibility features, but it is not accessible itself;
- accessible: the publication satisfies the requirements from the previous level, but it is also accessible according to Web Content Accessibility Guidelines (WCAG) and the requirements from this specification;
- optimized:the publication satisfies all requirements from the previous level, but also includes optimizations (and metadata about them) to provide an optimal reading experience for specific user groups (i.e. people with specific needs).