Plain English
Dense technical tools still need to be readable and operable.
Technical summary
Pages should use semantic headings, keyboard-reachable controls, visible focus, labeled form fields, and validation output that does not depend on color alone.
Deep spec
PUA previews need textual names and code point displays because many systems render private-use characters as blank boxes.
Tool UI requirements
- Every control has a visible label.
- Outputs update in an aria-live region.
- Warnings are text, not only color.
- Long code blocks and tables remain scrollable on mobile.