1. Overview
Principle 4 of WCAG 2.2 says that "content must be robust enough that it can be interpreted by a wide variety of user agents, including assistive technologies". It is the smallest principle. It has one guideline, 4.1 Compatible. After the removal of 4.1.1 Parsing, it has only two success criteria at Levels A and AA. It is also the principle that decides whether a screen-reader user can use your custom controls at all.
Take a visually perfect toggle built from a <div>. To VoiceOver, it is a piece of text that does nothing. What makes it a switch is the name, role and state exposed to the accessibility tree. That is what 4.1.2 asks for.
The word "robust" describes a relationship between three parties: the content, the browser (the user agent) and the assistive technology. The browser reads the HTML and builds an accessibility tree. The screen reader, voice-control software or switch interface reads that tree through the platform's accessibility services. If the tree says "button, Submit, dimmed", the assistive technology can present and operate the control. If it says "group, no name", nothing works, whatever the page looks like.
In EN 301 549, the two web criteria are clauses 9.4.1.2 and 9.4.1.3. Clause 9.4.1.1 is Void, with a note explaining why. So are clauses 10.4.1.1 and 11.4.1.1. For apps, clause 11.4.1.2 restates Name, Role, Value with one change of wording. Clause 11.5.2 lists the specific things an app must expose through the platform's accessibility services. Section 4 covers both.
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Sources
- W3C, Web Content Accessibility Guidelines (WCAG) 2.2, Principle 4, and the Understanding WCAG 2.2 documents for 4.1.2 and 4.1.3.
- W3C, Using ARIA (the first rule of ARIA), the Accessible Rich Internet Applications (WAI-ARIA) 1.2 specification and the ARIA Authoring Practices Guide patterns.
- ETSI, CEN and CENELEC, EN 301 549 V4.1.1 (2026-09), clauses 9.4, 10.4, 11.4 (including Table 11.17) and 11.5.2, available from the ETSI standards server.
- Directive (EU) 2019/882 (the European Accessibility Act), Annex I, Sections III and IV.
