Error Suggestion
When an input error is detected and a correction is known to the system, the system must offer a suggestion to the user — unless doing so would compromise security or invalidate the purpose of the input.
What it asks
When a form input is invalid and the system has enough information to propose a fix, it must offer that fix. “Date must be in DD/MM/YYYY format — did you mean 17/04/2026?” is better than just “Invalid date.” If the system knows valid options (e.g. nearest matching value, a list of allowed countries), it should surface them.
The SC has explicit exceptions: do not reveal information that would compromise security (don’t suggest a username when the real failure is a wrong password) and do not propose fixes that would defeat the input’s purpose (don’t auto-correct a CAPTCHA).
How to meet it
- For format errors, show the expected format and ideally re-format the user’s input as a suggestion: “Try 555-123-4567.”
- For typo’d email addresses, offer “Did you mean user@gmail.com?” when the entered domain is close to a known one.
- For invalid postal codes, suggest the closest match or display the valid format for the selected country.
- For password rules, list which specific rule failed: “Password must include a number — try adding a digit.”
- For out-of-range numbers, state the allowed range and offer the nearest valid value.
- Do not auto-apply suggestions silently — let the user accept or ignore.
Common failures
- Generic “Invalid input” messages with no hint about what valid input looks like.
- Password fields that say “Password does not meet requirements” without saying which rule failed.
- Address forms that reject a postal code without saying what format is expected for the selected country.
- Email validators that fail “user@gmial.com” silently with no suggestion of the likely typo.
Why it matters
Error suggestions are the difference between a user fixing a mistake in three seconds and abandoning the form. For users with cognitive disabilities, dyslexia, or motor difficulties, the cognitive load of figuring out what went wrong from a vague “Invalid” message is the actual barrier — not the typo itself.
Pair 3.3.3 with 3.3.1 and 3.3.2: identify what’s wrong, suggest how to fix it, and label the field clearly in the first place so the error becomes less likely.