Form Validation
Form validation uses rules and messages to find, prevent, and explain missing or wrong answers.
A real example
If a password breaks a rule, the page explains it beside the field. Screen readers can connect the message to that field.
Main parts
- 01State signal
- 02Human-readable message
- 03Timing or progress
- 04Recovery path
Use it when
Show help as soon as it's useful, and always check the answer again on the server.
Do not use it when
Never erase answers, blame people, or say only “invalid.” Explain how to fix the problem.
Name used in code
aria-invalid + server validation Before you ship
Before release, check the page structure, keyboard access, visible focus, contrast, and zoom. Also check loading, empty, error, success, cancel, and reduced-motion states.
Outcome: Use Form Validation to solve this user need without losing the current context. User context: If a password breaks a rule, the page explains it beside the field. Screen readers can connect the message to that field. Recommended pattern: Form Validation. Why it fits: Show help as soon as it's useful, and always check the answer again on the server. Do not use it when: Never erase answers, blame people, or say only “invalid.” Explain how to fix the problem. Product requirements: Define the default, loading, empty, error, success, and recovery states. Keep user input. Give clear feedback after every action. Accessibility and resilience: Use semantic HTML, full keyboard access, and visible focus. Make the layout work when zoomed and support reduced motion. Follow the project’s current rules. Do not add a new UI library unless the project already uses it. Acceptance criteria: The main task works with keyboard only and at 320px width. Focus and status changes are announced. Check loading, failure, retry, cancel, and reduced-motion paths. Evidence and limits (evidence boundary): The standard covers only the listed scope. It does not choose the visual style, product decision, or Vibulary example. Unknowns to confirm: Product wording, data source, analytics events, supported devices and languages, and platform limits.
Check this request
Review the current use of Form Validation. Definition: Form validation uses rules and messages to find, prevent, and explain missing or wrong answers. Release checks: Before release, check the page structure, keyboard access, visible focus, contrast, and zoom. Also check loading, empty, error, success, cancel, and reduced-motion states. Before changing code, report the evidence you found, gaps, severity, and the smallest safe fix.