Add a confirmation checkbox before final submission
G155 adds a checkbox the user must tick to say they have reviewed their input and are ready to commit it. W3C is specific about the shape. It loads unticked. It carries a label saying what is being confirmed, it sits near the submit button, and an unticked box means the submission is rejected and the user goes back to review. This is a sufficient technique for 3.3.4 Error Prevention at Level AA, which covers pages that create a legal commitment, move money, or delete data the user controls. Five techniques answer that rule and W3C ranks none of them. A checkbox is one honest way to slow the final step down. Reviewing before submitting, being able to undo afterwards, and stating a cancellation window are others, and the right one depends on the transaction.
How we find it in an audit
Our reviewers list every irreversible action on the site first, since that is what the rule covers. Then we walk each one to the point of no return. Does anything sit between intent and commitment? We check that the confirmation names the consequence rather than asking a vague are-you-sure, and that it is reachable and operable from the keyboard.
How affected users experience it
Screen reader and switch users trigger the wrong control more often than anyone else, because their route to a button runs through more steps and more chances to slip. Someone with a motor disability may fire a click they never intended. A deliberate second act, with a label that says what is about to happen, converts a mistake that cannot be undone into one that never gets made.
Passes vs. fails
Passes
Filing requires ticking 'I have reviewed this return and I am ready to file' before the Submit button will act.
Fails
One press of 'Submit' files the tax return instantly, with no step to catch that it is the wrong year's form.
Other ways to satisfy this rule
7 guides on this site are filed under 3.3.4 Error Prevention (Legal, Financial, Data). W3C lists this one as sufficient for that rule on its own. Implement it correctly, in a way your readers' software actually supports, and the rule is met.
- G98sufficientLet users review answers before final submission
- G99sufficientMake deleted data recoverable
- G164sufficientState how long requests can be canceled
- G168sufficientAsk for confirmation before completing risky actions
- G199advisoryConfirm success when a submission works
- SCR18advisoryValidate in the browser and describe the error
This guide is our interpretation of W3C technique G155: Providing a checkbox in addition to a submit button. W3C publishes its techniques as guidance rather than as the standard, and says so on every one of them. The success criterion is what conformance is measured against, and a technique is one documented way to meet it.