# Understanding Error Identification

## In brief

Goal
  Users know an error exists and what is wrong.
What to do
  Provide descriptive notification of errors.
Why it's important
  Flagging errors helps people with reduced sight and cognitive disabilities resolve them.

## Intent of Error Identification

The intent of this success criterion is to ensure that users are aware that an error has occurred and can determine what is wrong. In the case of an unsuccessful form submission, it is not sufficient to only re-display the form without providing any hint that the submission failed. The error must be indicated in text. Whether or not an error message provides users with sufficient information about the nature of the error, and what they should do to correct it, is covered more specifically by 3.3.3 Error Suggestion.

An "input error" is information provided by the user that is not accepted. This includes:

- information that is required by the web page but omitted by the user, or
- information that is provided by the user but that falls outside the required data format or allowed values.

For example:

- the user fails to enter the proper abbreviation in a state, province, or region field;
- the user enters a state abbreviation that is not a valid state;
- the user enters a non existent zip or postal code;
- the user enters a birth date 2 years in the future;
- the user enters alphabetic characters or parentheses into their phone number field that only accepts numbers;
- the user enters a bid that is below the previous bid or the minimum bid increment.

If a user enters a value that is too high or too low, and the coding on the page automatically changes that value to fall within the allowed range, the user's error would still need to be described to them as required by the success criterion. Such an error description telling the person of the changed value would meet both this success criterion (Error Identification) and 3.3.3 Error Suggestion.

The identification and description of an error can be combined with programmatic information that user agents or assistive technologies can use to identify an error and provide error information to the user. For example, certain technologies can specify that the user's input must not fall outside a specific range, or that a form field is required. Currently, few technologies support this kind of programmatic information, but this success criterion does not require, nor prevent it.

It is perfectly acceptable to indicate the error in other ways such as through the use of an image, color, or other visual indicator, in addition to the text description.

This criterion does not mandate any particular way in which errors should be displayed. Depending on the situation, it may be more suitable for all errors to be listed at the start or before a form. In other cases, it may be more appropriate to show errors inline, with error messages next to the specific fields that are in error. Errors could also be listed in an alert, or dialog. This criterion does not cover which of these methods should be used - the only requirement is for errors to be presented to users in text or a text alternative.

See also 3.3.3: Error Suggestion.

## Benefits of Error Identification

- Providing information about input errors in text allows users who are blind or color deficient (color blind) to perceive the fact that an error occurred.
- This success criterion may help people with cognitive, language, and learning disabilities who have difficulty understanding the specific reason why a form submission failed (in cases where this is not already made obvious by the nature of the form).

## Examples of Error Identification

Identifying errors in a form submission

  An airline Web site offers a special promotion on discounted flights. The user is asked to complete a simple form that asks for personal information such as name, address, phone number, seating preference and e-mail address. If any of the fields of the form are either not completed or completed incorrectly, an alert is displayed notifying the user which field or fields were missing or incorrect.

  This success criterion does not mean that color or text styles cannot be used to indicate errors. It simply requires that errors also be identified using text.

Providing multiple cues
  The user fails to fill in two fields on the form. In addition to describing the error and providing a unique character to make it easy to search for the fields, the fields are highlighted in yellow to make it easier to visually search for them as well.

## Resources for Error Identification

## Techniques for Error Identification

### Sufficient Techniques for Error Identification

#### Situation A: If a form contains fields for which information from the user is mandatory.

- Providing a text description that identifies the field as mandatory
- ARIA2: Identifying required fields with the "required" property
- Providing client-side validation and alert

#### Situation B: If information provided by the user is required to be in a specific data format or of certain values.

- G84: Providing a text description when the user provides information that is not in the list of allowed values
- Providing a text description when user input falls outside the required format or values
- Providing client-side validation and alert
- Providing client-side validation and adding error text via the DOM

### Additional Techniques (Advisory) for Error Identification

- G139: Creating a mechanism that allows users to jump to errors
- Providing success feedback when data is submitted successfully

### Failures for Error Identification