Using aria-describedby to provide descriptions of images

Status

• Surveyed by TF 25 June 2012
• Discussed by TF 25 June 2012
• Reopening to address Laura Carlson's comment, surveyed in Responses to Public Comments, ARIA Techniques and review of images section of WAI tutorials. August 20th 2013
• Discussed October 8 and this technique updated to adhere with response to Laura Carlson's comment LC-2848 and John Foliot's comment LC-2847. Will be confirmed on the November 26 survey.
• Added to XML by AWK 2014/1/2

Using ARIA Describedby to provide descriptions of images

User Agent Notes [To be published separately]

Updated by David MacDonald July 16, 2013

• Jaws V.11 and greater has complete support. IE10 JAWS 14. Speaks alt and then "press JAWS key + alt +r to hear descriptive text". IE 10 intermittent support, sometimes works, sometimes need to reload the page for JAWs to read it properly.
• ChromeVox V.1 and greater has complete support?
• VoiceOver V.3 and greater supports but replaces ALT text if both are present
• NVDA 2 reads ALT text if both are present but not Describedby unless it is alone
• Window Eyes as of V.7 ???.

Applicability

As of this writing this technique applies to HTML technologies.

This technique relates to:

• Success Criterion 1.1.1 (Text Alternatives)

Description

The objective of this technique is to provide descriptions of images when a short text alternative does not adequately convey the function or information provided in the object.

A feature of WAI-ARIA is the ability to associate descriptive text with a section, drawing, form element, picture, and so on using the aria-describedby property. This is similar to the longdesc attribute in that both are useful for providing additional information to help users understand complex images. Like longdesc, descriptive text provided using aria-describedby is separate from the short name provided using the alt attribute in HTML. Unlike longdesc, aria-describedby cannot reference descriptions outside of the page containing the image. An advantage of providing long descriptions using content from the same page as the image is that the alternative is available to all, including sighted people who do not have assistive technology. It is worth noting that as of the time of writing (October 2013) some assistive technologies read aria-describedby content immediately after an image's alt attribute information without user activation - whereas most implementations of longdesc require the user to take explicit action to read the additional description.

Like aria-labelledby, aria-describedby can accept multiple ids to point to other regions of the page using a space separated list. It is also limited to ids for defining these sets.

Examples

Example 1

The following example shows how aria-describedby can be applied to an image to provide a long description, where that text description is on the same page as the image.

<img src="ladymacbeth.jpg" alt="Lady MacBeth" aria-describedby="p1">
<p id="p1">This painting dates back to 1730 and is oil on canvas. It was created by 
Jean-Guy Millome, and represents ...</p>

Resources

• WAI ARIA 1.0 Authoring Practices
• HTML to Platform Accessibility APIs Implementation Guide: Accessible Name and Description Calculation

Related Techniques

• ARIA-XX: Using aria-labelledby to provide labels for objects.
• ARIA-XX: Using aria-label to provide labels for objects.
• G92: Providing long description for non-text content that serves the same purpose and presents the same information
• H45: Using longdesc

Tests

Procedure

1. Examine each image element where a aria-describedby attribute is present.
2. Examine whether the aria-describedby attribute programatically associates an element with its text description, via the id attribute on the element where the text to be used as the description is found.
3. Examine whether the combined text equivalent and associated text description accurately describe or provide the equivalent purpose to the object.

Expected Results

Tests #1, #2 and #3 are true.