The guideline
Mark every field's required/optional status explicitly and visibly — not only the required ones, since a form with asterisks on some fields leaves every unmarked field ambiguous. Pick one convention (mark optional fields with the word "(optional)" and state once that everything else is required; or mark required fields with an asterisk plus a visible legend explaining it) and apply it identically across the whole form. Add the native required attribute, or aria-required="true" on custom controls, alongside the visual marker so the status is announced to assistive technology, not only shown.
Common failures
- The form does not clearly distinguish which fields are mandatory and which are optional, forcing users to guess or discover requirements only after attempting to submit. This creates unnecessary friction at a critical step.
Where it applies
Pages
Disciplines
Devices
Why it matters, how to fix it, and the research behind it
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