Accessibility Coding Standards 
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Code integrated into the WordPress ecosystem – including WordPress core, WordPress.org websites, and official plugins, is expected to conform to the Web Content Accessibility Guidelines (WCAG), version 2.1, at level AA.
New or updated interfaces are encouraged to incorporate the Authoring Tool Accessibility Guidelines (ATAG) 2.0. The most significant way that ATAG 2.0 guidelines can be incorporated is by emphasizing choices that help people make more accessible content: encouraging alternative text, captions, and semantic structures, for example.
Official information about web accessibility standards can be divided into two groups: “normative” and “informative” documents. Only the guidelines themselves are normative, and establish the actual requirements for conforming to WCAG 2.1. Other documents should be considered to be informational, and offer help in interpreting the guidelines, but are not definitive.
The WordPress A11y team is in the process of developing a library of recommended accessibility patterns to help describe the WordPress recommended way to accomplish a variety of interfaces. These may not be the only reasonable way to create an accessible example of the pattern, but are preferred for the sake of consistency across WordPress.
Normative Documents:
– W3C WCAG 2.1
– W3C ATAG 2.0
– W3C WAI ARIA 1.1
Informative Documents:
– W3C Understanding WCAG 2.1
– W3C Using ARIA
– W3C WAI-ARIA Authoring Practices 1.1 (accessible design patterns)
– W3C Introduction to ATAG
About WCAG A, AA, and AAA Conformance Levels About WCAG A, AA, and AAA Conformance Levels
The WordPress commitment is to conform to all WCAG 2.1 Level A and Level AA guidelines. Conformance to level AAA success criteria is encouraged where relevant, as is exceeding the accessibility of any of these guidelines.
Level A success criteria address concerns considered to be accessibility barriers on a very wide scale that will prevent many people from accessing the site and the minimum set of accomplished goals required for the majority of web-based interfaces.
Level AA success criteria address concerns that are generally somewhat more complicated to address and may impact smaller groups of people, but are still common needs with broad reach.
Level AAA success criteria are mostly targeted at very specific needs and may be quite difficult to implement effectively.
W3C Quick Reference to WCAG 2.1 Level A and Level AA Requirements
Applying WCAG Conformance Levels Applying WCAG Conformance Levels
WCAG 2.1 consists of 4 layers:
– Principles
– Guidance
– Success criteria
– Sufficient and advisory techniques
Principles Principles
When applying WCAG 2.1, the guidance and success criteria are organized around 4 principles. These principles place emphasis on how people interact with content and must be:
– Perceivable – interacting with the content using the medium that they are familiar with. For example, providing text alternatives for those who are blind.
– Operable – finding and using content is accessible. For example, being able to use a keyboard or a screen reader.
– Understandable – content uses clear language and is understandable. For example, use meaningful labels, explain all abbreviations.
– Robust – content can be interpreted in a range of ways. For example, assistive technologies are able to interpret and parse content.
Guidance Guidance
Each principle is supported by a list of guidelines to ensure that content is more accessible and presentable across the different devices that meet a user’s disability. The guidelines are listed below, the full detail can be found in the WCAG 2.1.
Principle: Perceivable Principle: Perceivable
Guideline 1.1 Text Alternatives
Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.
Guideline 1.2 Time-based Media
Provide alternatives for time-based media. For example, include captions and transcripts for audio or video clips.
Guideline 1.3 Adaptable
Create content that can be presented in different ways (for example simpler layout) without losing information or structure.
Guideline 1.4 Distinguishable
Make it easier for users to see and hear content including separating foreground from background.
Principle: Operable Principle: Operable
Guideline 2.1 Keyboard Accessible
Make all functionality available from a keyboard.
Guideline 2.2 Enough Time
Provide users enough time to read and use content.
Guideline 2.3 Seizures and Physical Reactions
Do not design content in a way that is known to cause seizures or physical reactions.
Guideline 2.4 Navigable
Provide ways to help users navigate, find content, and determine where they are.
Guideline 2.5 Input Modalities
Make it easier for users to operate functionality through various inputs beyond keyboard.
Principle: Understandable Principle: Understandable
Guideline 3.1 Readable
Make text content readable and understandable.
Guideline 3.2 Predictable
Make Web pages appear and operate in predictable ways.
Guideline 3.3 Input Assistance
Help users avoid and correct mistakes.
Principle: Robust Principle: Robust
Guideline 4.1 Compatible
Maximize compatibility with current and future user agents, including assistive technologies.
Success Criteria Success Criteria
Each guidance has a specific list requirements that must be met for your content to be accessible. These tests can be carried out using automated software and or human testers. You can find more information on how to meet the success criteria in Understanding Levels of Conformance. Whilst these criteria are important, usability testing is still important and should be carried out alongside any accessibility testing.
Techniques: Sufficient, Advisory, and Failures Techniques: Sufficient, Advisory, and Failures
Techniques (code examples, resources, and tests) for guidance and success criteria that can help in making content more accessible, are divided into three categories:
– Sufficient – required and help meet the success criteria
– Advisory – suggestions and go beyond what is required
– Failures – cause problems and fail to meet the success criteria
For more information on techniques, visit Understanding Techniques for WCAG Success Criteria.
Authoritative Resources Authoritative Resources
- WebAIM: Web Accessibility In Mind (see Articles and Resources)
- Government Digital Service
- Accessibility in government
- Blog | TPG – The Accessibility Experts
- Web Accessibility Blog (Deque)
- Tink – Léonie Watson (Léonie Watson)
- Adrian Roselli
- Scott O’Hara
- Joe Dolson
- Sarah Higley
- Marco’s Accessibility Blog
- Karl Groves
- Inclusive Components (Heydon Pickering)
- Accessibility London (London, United Kingdom) (London accessibility meetup: they live stream meetups on youtube)
- 24 Accessibility
- Mozilla Accessibility – Users first, no matter their abilities
Technical and / or specific topics: Technical and / or specific topics:
- Accessibility Support (Will your code work with assistive technologies?)
- Accessibility APIs: A Key To Web Accessibility (by Léonie Watson)
- How accessibility trees inform assistive tech (by Hidde de Vries)
- What is this thing and what does it do? (presentation by Karl Groves)
- The Browser Accessibility Tree (by Steve Faulkner)
- Brief history of browser accessibility support (by Steve Faulkner)
- ARIA Landmarks Example: General Principles
- ARIA Landmarks Example: HTML Sectioning Elements