W3C Approves Longdesc

Submitted by Geoff Freed

After years of debate, the longdesc attribute has been approved as an extension to the W3C’s HTML5 recommendation.  The new extension is available at http://www.w3.org/TR/2015/REC-html-longdesc-20150226/, and it defines a simple method of associating long descriptions with images.  The longdesc attribute is not new— it was originally included in HTML 4.0— but it was removed from HTML5 because of disagreement about its effectiveness.  Its (re)approval by the W3C now means that authors can continue to use it to provide long image descriptions in a standards-compliant manner.  The presence of longdesc-delivered descriptions is announced by JAWS, NVDA, Window-Eyes and ChromeVox screen readers (VoiceOver does not currently recognize the longdesc attribute), and longdesc is supported by Firefox, IE and Chrome browsers.  Other assistive technologies may provide support for longdesc as well.  Additionally, by downloading and installing the Firefox longdesc extension, sighted users can right-click on an image and see a menu choice for viewing the associated long description.

The longdesc attribute is, however, not the only means by which long image descriptions can be delivered to users.  Other methods include:

• the use of ARIA properties, such as aria-describedby and aria-describedat (still under development)
• the <details> element or hidden iframes (examples at http://cookiecrook.com/longdesc/)
• Diagrammar (introduction and examples at http://diagramcenter.org/standards-and-practices/content-model.html)
• integrating image descriptions into the body of the document itself

To see the refreshed recommendations on when to use the longdesc attribute from the DIAGRAM Standards Working Group, please visit http://diagramcenter.org/standards-and-practices/html-standards.html.