3.3.6 Error Prevention (All)

1. What is the goal of this criterion?

One wrong click, a transposed digit, an overlooked required field – we all know the frustration of a form blowing up in our face. But while many people can simply go back and fix things, for people with disabilities it often becomes a real problem. People with motor impairments mistype more easily, people with cognitive disabilities are more likely to miss important details, and people with visual impairments find it harder to spot errors.

So the goal of WCAG Success Criterion 3.3.6 is clear: every form – not just those with legal or financial consequences – needs a safety net. It’s about catching mistakes before they take effect, or being able to undo them if they do happen.

2. What exactly does it require?

While Error Prevention (Legal, Financial, Data) only applies to legally or financially relevant actions, changing or deleting data, and submitting tests, 3.3.6 goes one step further: for every page that requires you to submit information, at least one of these three options must be met:

Reversible: you can undo a submission after sending it – for example with an “Undo” button or a trash folder for deleted content.

Checked: the system automatically checks the data you entered for errors and gives you the chance to correct them.

Confirmed: there’s a step in which you can review, confirm and correct your details before they’re finally submitted.

The criterion applies to all forms – from a simple newsletter sign-up to a complex order. Level AAA makes it clear: this is the premier league of accessibility, but also a genuine quality benchmark for user-centred design.

3. Why does it matter for accessibility?

Imagine trying to type your address into a form, but your fingers don’t always hit the right keys. Or you’re filling in a complex form and miss an important detail because your attention quickly fades. Without a safety net, this gets frustrating – or can even stop you from using the service at all.

Error prevention supports accessibility because it:

• helps people with motor impairments correct accidental input errors
• gives people with cognitive disabilities more time and more ways to check their input
• helps people with attention deficits avoid missing important details
• lets people with visual impairments double-check their input
• gives everyone more confidence and trust when filling in forms

And last but not least: it reduces stress and makes using your website more relaxed.

4. How to meet the criterion

The good news: you already know many of these features from other websites – now it’s about using them deliberately and systematically. Here are proven strategies for each of the three options:

Undo features:

• Add “Undo” buttons for important actions like deleting or moving
• Offer a trash folder for deleted content with a restore option
• Allow entries to be edited after the first submission (e.g. profile data or comments)
• As a useful extra: save progress automatically so nothing is lost if something goes wrong

Checking and validation:

• Validate input in the browser, ideally when a field is left or on submission
• Provide helpful error messages with concrete suggestions (see Error Identification and Error Suggestion)
• Clearly mark fields in error and explain what needs fixing
• Use format hints (e.g. for phone numbers: “+49 30 1234567”)

Confirmation steps:

• Show a summary of all input before final submission
• Allow individual sections to be edited directly from the summary
• Use clear “Back” and “Edit” buttons
• Make the final “Submit” button unambiguous so it’s clear this is the binding step

General tips:

• Combine several approaches for critical forms
• Test your forms with real users, especially people with disabilities
• Think about mobile – typos happen more easily on small screens

5. Why this criterion matters for businesses

With Success Criterion 3.3.6, too, accessibility isn’t an end in itself – it’s a real competitive advantage for your business.

1. Reach a wider audience

Forms are often the decisive point where visitors become customers. If people with disabilities fail at your forms, that’s exactly where you lose them. In Germany alone, around 7.9 million people with severe disabilities were living at the end of 2023, according to the Federal Statistical Office (Destatis).

2. Fewer drop-offs

Forms in which mistakes are easy to spot and fix lead to fewer drop-offs and more completions, because people trust the process.

3. Lower support costs

Fewer errors mean fewer support requests. When people can correct their input themselves instead of contacting customer service, you save time and money – and the experience improves at the same time.

On the legal side: 3.3.6 is a Level AAA criterion and isn’t explicitly required by the European Accessibility Act or its German implementation, the Barrierefreiheitsstärkungsgesetz (BFSG) – the harmonised standard EN 301 549 refers to WCAG 2.1 Level AA for web content. Error Prevention (Legal, Financial, Data), on the other hand, is required; 3.3.6 extends the same principle to all forms. This section is general information, not legal advice.

6. The success criterion in the W3C’s words

Success Criterion 3.3.6 Error Prevention (All) (Level AAA)

For web pages that require the user to submit information, at least one of the following is true:

• Reversible: Submissions are reversible.
• Checked: Data entered by the user is checked for input errors and the user is provided an opportunity to correct them.
• Confirmed: A mechanism is available for reviewing, confirming, and correcting information before finalizing the submission.

In short: on every page where you submit information, the submission is reversible, checked, or can be reviewed and confirmed beforehand.