Technologies that support Accessible Rich Internet Applications (WAI-ARIA).
This technique relates to:
See User Agent Support for WAI-ARIA for general information on user agent support.
Updated 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 ???.
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.
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 are for information purposes only, no endorsement implied.
Examine each image element where a aria-describedby
attribute is present.
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.
Examine whether the combined text equivalent and associated text description accurately describe or provide the equivalent purpose to the object.
#1, #2, and #3 are true.
If this is a sufficient technique for a success criterion, failing this test procedure does not necessarily mean that the success criterion has not been satisfied in some other way, only that this technique has not been successfully implemented and can not be used to claim conformance.
Techniques are informative—that means they are not required. The basis for determining conformance to WCAG 2.0 is the success criteria from the WCAG 2.0 standard—not the techniques. For important information about techniques, please see the Understanding Techniques for WCAG Success Criteria section of Understanding WCAG 2.0.