WCAG Guidelines
Web Content Accessibility Guidelines (WCAG) - currently at version at version 2.1 - are freely available online at
"WCAG 2.1 success criteria are written as testable statements that are not technology-specific... and testable with a combination of automated testing and human evaluation."
This version of the WCAG aimed to expand the definitions to include "criteria to address cognitive, language, and learning disabilities" however significant challenges remain and will be the subject of future work.
WCAG describes three levels of testable conformance with the guidelines for accessibility: A (lowest), AA, and AAA (highest). https://www.w3.org/WAI/WCAG21/Understanding/conformance#levels
One of the most enabling resources an author, publisher, developer can provide for accessibility is to offer metadata for objects. Metadata is 'data about data', descriptive text, alternate text, transcripts of recordings, visual captioning, audio captioning, and many other approaches. Metadata should be machine readable for users of assistive devices to translate or represent the data in the desired format. https://www.w3.org/WAI/WCAG21/Understanding/understanding-metadata
The WCAG provides an extensive library of techniques and design principles for developers and content publishers to apply.
https://www.w3.org/WAI/WCAG21/Techniques/
These web-centric techniques and technologies range over
- General Techniques for Web Page Design
- CSS Techniques
- HTML Techniques
- PDF Techniques
- Plain-Text techniques and technologies
- Synchronized Multimedia Integration Language (SMIL) technology (like .vtt - video text track files)
- Accessible Rich Internet Applications (ARIA)
- And design architectural guidelines for Client-Side Scripting, Server-Side Scripting
- With commentary on negative criteria or Failure Modes
Further Reading
For more see "How People with Disabilities Use the Web" and in particular review the "Stories of Web Users" for Personas being applied https://www.w3.org/WAI/people-use-web/
