Error Prevention (All)
For any user submission — not just legal, financial, or data-changing ones — the user must be able to reverse, check, or confirm before the submission takes effect. The AAA generalisation of 3.3.4.
What it asks
This is the AAA generalisation of 3.3.4: the same three protections (reversible, checked, or confirmed) apply to every submission the user can make on the page, not only to legal, financial, or data-changing ones. Newsletter signups, comment posts, form submissions of every kind get the same safety net.
How to meet it
- Show a preview before sending a long message, comment, or post.
- Allow the user to edit submitted comments or messages for a short window.
- For multi-step forms, allow the user to navigate back and review every step before the final submit.
- Show a confirmation toast with an “Undo” affordance for as many actions as practical.
- For “Send” buttons in messaging UIs, optionally implement an unsend window (Gmail’s “Undo send” pattern).
Common failures
- Comment forms that post immediately on submit with no edit window.
- Newsletter subscriptions that fire confirmation emails before showing a preview of what the user is signing up for.
- Forum posts that publish immediately, with no review step or grace period for typos.
- Reaction or rating widgets that commit on first click with no way to change the rating.
Why it matters
This is AAA and uncommonly a compliance target, but the design principle behind it — let users review, undo, or confirm — is universally beneficial. Users with motor disabilities, tremor, or cognitive disabilities are more likely to misfire, and they bear the highest cost when there is no safety net. Even for everyone else, a good undo affordance is one of the cheapest UX upgrades you can ship.