4.1 Compatible · Robust
WCAG 4.1.1 Parsing
Level A
Markup must have no parsing errors that affect assistive tech (duplicate IDs, unclosed tags). Note: this criterion was withdrawn in WCAG 2.2; still in 2.1.
Common failures
- Duplicate `id` attributes break ARIA reference relationships.
- Unclosed tags confuse legacy assistive tech.
How to fix
- Run an HTML validator in CI.
- Avoid manual ID juggling — generate unique IDs.
Related criteria
- WCAG 4.1.2 Name, Role, Value Level A