- Required and optional fields are both marked, consistentlyUsually highMark every field's required/optional status explicitly and visibly — not only the required ones, since a form with asterisks on some fields leaves every…
- Error messages name the field, the problem, and the fixUsually mediumWrite every error message to do three things: identify which field failed, state what is wrong with it in plain language, and say what a valid value looks like.
Why it matters, how to fix it, and the research behind it
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