WCAG 3.3.4 Error Prevention (Legal, Financial, Data)

Success criterion 3.3.4 protects people from costly mistakes they cannot undo. Someone with a reading disability may transpose digits in a quantity, someone with a motor disability may hit the wrong button, and a screen reader user may not notice that the wrong size was selected. When the result is a paid order or a deleted account, the consequences are real. It is level AA and appears in EN 301 549 as clause 9.3.3.4.

What the criterion requires

The criterion applies to web pages that:

• cause legal commitments or financial transactions for the user (placing an order, accepting a contract, paying);
• modify or delete user-controllable data in data storage systems (account details, addresses, saved data);
• or submit user test responses.

For these pages, at least one of the following must be true:

1. Reversible: the submission can be reversed, for example cancelled within a stated time.
2. Checked: the data entered is checked for input errors and the user gets an opportunity to correct them.
3. Confirmed: a mechanism is available to review, confirm and correct the information before the submission is finalised.

The criterion is aimed at serious mistakes. It does not ask for a confirmation on every save or edit.

Typical failures on an online shop

Each of these fails only when none of the three options is offered — for example, when the order also cannot be cancelled:

• "Buy now" or one-click buttons that place a paid order immediately, with no review step and no way to cancel;
• a checkout where the final step does not show the items, quantities, address and total before payment;
• an order summary that cannot be edited — users must start over to change an address;
• "Delete account" or "Remove all saved addresses" that runs at once with no confirmation or undo;
• a subscription signup that commits to recurring payments without showing the terms before confirmation.

How to check it

Automated: our checker has no rule for this criterion. It does not place orders or delete data, so this needs a manual check.

By hand: go through the purchase flow with a test product and stop before paying. Check whether you can see and change everything — items, quantity, delivery address, delivery method, total — before the final button. Then check the account area: delete an address or the account and see whether there is a confirmation, a check or an undo. Note the cancellation options offered after an order.

How to fix it

• Add a review step, or make the last checkout step show all order details with "Edit" links.
• Use a clear final button such as "Place order and pay", separate from "Continue".
• Ask for confirmation before deleting accounts or data, or offer a restore option.
• Validate input (address, card, quantity) and let users correct it before the order is placed.

Related criteria

• 3.3.1 Error Identification — errors are identified in text.
• 3.3.3 Error Suggestion — users are told how to fix errors.
• 3.3.7 Redundant Entry — don't make users retype data in the same process.

Frequently asked questions

Does every checkout need a review page?

No. 3.3.4 asks for at least one of three options: the submission is reversible, the data is checked and the user can correct it, or there is a way to review and confirm before finalising. A review step is one common way.

Does 3.3.4 apply to deleting an account or an address?

Yes. Pages that modify or delete user-controllable data in data storage systems are in scope, so deleting an account, saved address or wishlist should be reversible, checked or confirmed.

Does 3.3.4 require a confirmation dialog for every save?

No. W3C explains that it is about preventing serious, hard-to-reverse mistakes such as mass data loss, not about confirming every edit.