WCAG 2.1 SC 3.3.4: Error Prevention (Legal, Financial, Data) (Level AA)
3.3.4 Error Prevention (Legal, Financial, Data) (Level AA) — what it requires, a common failure example, and how to fix it. Part of WCAG 2.1's 3.3 Input Assistance guideline under the Understandable principle.
WCAG 2.1 guidelines hub → Understandable → 3.3 Input Assistance
3.3.4 Error Prevention (Legal, Financial, Data) (Level AA)
Input Assistance is the guideline most directly relevant to checkout and account forms — it governs whether people can tell what a field wants, whether errors are described clearly, and whether a costly mistake (an accidental purchase, a wrong shipping address) can be caught before it’s final.
This page is educational technical reference material, not legal advice. Meeting WCAG 2.1 does not by itself determine legal compliance with the ADA or any other law — consult qualified counsel for legal risk questions.
Plain-language explanation: For submissions that create a binding legal or financial obligation — completing a purchase, for example — the user needs a way to review, correct, or confirm before it’s final, or the action needs to be reversible.
Common failure: Clicking “Place Order” charges the card and confirms the order in one irreversible step, with no review screen showing the final total, shipping address, and items before the charge goes through.
Remediation: Add a review/confirmation step between “submit” and “final commit” showing exactly what will happen, or make the action reversible for a defined window after submission (e.g. an order-edit or cancellation grace period).
In this guideline — 3.3 Input Assistance: 3.3.1 Error Identification (A) · 3.3.2 Labels or Instructions (A) · 3.3.3 Error Suggestion (AA) · 3.3.4 Error Prevention (Legal, Financial, Data) (AA) · 3.3.5 Help (AAA) · 3.3.6 Error Prevention (All) (AAA)
← Previous: 3.3.3 Error Suggestion (AA) · Next: 3.3.5 Help (AAA) →
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This page is educational content about technical accessibility practice, not legal advice. Meeting WCAG 2.1 does not guarantee legal compliance with the ADA or any other law. Consult qualified counsel for legal risk questions.
This page was drafted with AI assistance and reviewed by a person for accuracy before publication.