errors

GUIDELINES 3.3

Overview

Error prevention goes beyond correcting mistakes after they happen. For submissions involving legal commitments, financial transactions, or personal data, users must be able to review, correct, and confirm their input before it is finalized.

Who is impacted

Users with cognitive disabilities, attention difficulties, or motor impairments who are more likely to make input errors and may struggle to recover from irreversible submissions.

How to test

Complete a form submission involving sensitive data and verify that the interface provides at least one of the following: a confirmation step before finalizing, the ability to review and edit before submitting, or a way to reverse or cancel the submission afterward.

Resources

Visit W3C Understanding Error Prevention and WebAIM Creating Accessible Forms for detailed guidance.

Error Prevention vs Error Correction

Error correction (covered under WCAG 3.3.1 and 3.3.3) is about identifying mistakes and helping users fix them in real time. Error prevention under WCAG 3.3.4 is a higher standard that applies specifically to consequential actions. If a user is submitting a purchase, signing a legal agreement, or modifying account data, catching a typo after the fact is not enough. The system itself must be designed to make irreversible errors hard to commit.

How to Implement Error Prevention

The most common approach is a confirmation or review step before final submission. Show users a summary of what they are about to submit and ask them to confirm. For financial or legal forms, include a checkbox requiring explicit acknowledgment before the submit button becomes active. Where possible, allow users to cancel or undo a submission within a reasonable window after it completes. Autosave drafts and session persistence also reduce the risk of data loss from accidental navigation away from a form.