ACT-R2: Proper use of aria-describedby

Important Information for reviewing ACT Rules

Important: The ACT Rules on this page are a demonstration of how they might be published by the W3C. The goal of this page is to add concrete examples for the Accessibility Conformance Testing Rules Format (DRAFT). Neither the ACT Rules, or the way they are presented here has been approved by the Accessibility Guidelines Working Group. If you have feedback, please comment by filing GitHub issues in the WCAG ACT repository, if this is not feasible, by email to public-wcag-act-comments@w3.org.

Accessibility Requirements

This conformance rule relates to:


This rule checks the sufficient provision of a long text description for images that are using the aria-describedby attribute.

Elements are not checked for references to long text descriptions within short text alternatives such as “The image is described in text below”.


This rule maps to WCAG 2.0 success criterion 1.1.1 and checks the following techniques and failures:


Aspects Under Test

Test Procedure


This rule applies to any element with a semantic role of img that has a non-empty aria-describedby attribute and is perceivable by assistive technologies.

Expectation 1

For each target element, at least one of the identifiers in the aria-describedby attribute is a valid identifier.

Expectation 2

For each target element that fulfills Expectation 1, at least one of the elements referenced by the aria-describedby attribute exists.

Expectation 3

For each target element that fulfills Expectation 2, the accessible description provides an extended description of the image complementing the accessible name.


This rule is an example, precise definitions will be added before publication.


Changes since the previous version


This ACT rule was created by Frank Berker and Kasper Isager.

Validation Tests

To validate the implementation of this rule, all test cases for ACT-R2 must be passed.