3. Understandable

3.3 Input Assistance (Level A)

Guideline 3.3 Input Assistance

Help users avoid and correct mistakes.

What is “input assistance?” How does it support understandability?

“Input assistance” is WCAG 2.1 jargon for techniques that help people avoid mistakes, especially when filling out forms. When people do make mistakes, it refers to the techniques that help them recover from errors.


Input assistance: Techniques that encourage users to understand the process of entering information. These techniques include providing clear instructions, a chance to check work before submitting it, and context-sensitive help.

Everyone makes mistakes, but some people with disabilities may be more prone to input errors than people without disabilities. For example, someone with a tremor may press keys by accident. An individual who is blind may have trouble determining which fields are mandatory and which are optional. A person who relies on speech recognition software may produce words that are different than the dictated words.

This guideline seeks to reduce the number of serious errors that users make, increase the likelihood that users will notice their errors, and help users understand what they must do to correct errors.

Success Criterion 3.3.1 Error Identification

Level A

If an input error is automatically detected, the item that is in error is identified and the error is described to the user in text.

Error Identification Explained

When designing a website or online form, use text to indicate and describe errors.

It is okay to signal errors with images and colour changes provided there are also text descriptions.

Example: A bank encourages customers to apply for loans online. A customer submits a form with his or her name, address, phone number, email address, and account number. If the customer does not complete the form correctly, the form is re-displayed with an alert — three question marks ??? displayed after the prompt — for all missing or incorrect fields.

In addition, the fields in error are highlighted yellow to make them easier to spot.

SC 3.3.1 is a special benefit to screen reader users. Since screen readers only read text, screen reader users may have trouble understanding non-text error messages.

Suggested Reading:

Success Criterion 3.3.2 Labels or Instructions

Level A

Labels or instructions are provided when content requires user input.

Labels or Instructions Explained

When designing online forms, help users enter information by providing clear instructions and examples. Conformance to SC 3.3.2 helps users avoid mistakes when their input is required.

When filling out forms, people who use certain assistive technologies are more likely to make mistakes than users without disabilities. Similarly, when recovering from mistakes, these users may have trouble focusing in on and fixing problems.

Instructions and cues that are visually and programmatically connected to form controls help users complete forms successfully the first time. If they do make mistakes, instructions and cues make it easier to find and fix them.

Examples of providing clear cues and instructions:

  • Use Given Name instead of Name 1 as the prompt for entering a first name, and Family Name instead of Name 2 for entering a surname.
  • Show the required date format for a field: Date (dd-mm-yyyy).
  • Place prompts for text fields and combo boxes above or to the left of controls, and place prompts for checkboxes and radio buttons to the right of controls. Doing this “automatically” produces fairly accessible form controls.

Suggested Reading:


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Introduction to Web Accessibility Copyright © 2019 by The Chang School, Toronto Metropolitan University is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License, except where otherwise noted.

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