DEV 6.2 - Provide full descriptions for informational images

Complex images such as charts, diagrams and graphs need more description than an alt attribute alone can reasonably display.

  • Add a longer description:
    • on the same page, near the image (recommended);
    • On a separate page, linked using:
      • a normal text link to the description,
      • longdesc to point to the URL,
      • A '[d]' link placed after the image to point to the URL (use a normal link if possible - the use of [d] links is becoming less common and less well known.)
  • If providing a description on a separate page, the resulting linked page should contain all of the following:
    • a clear title
    • An appropriate description of the complex image;
    • A link back to the original page.
  • The description should convey the essential information that you are trying to provide by including the image - don't over do it if unnecessary, for example for a graph:
    • 'Trend in ...:
      • describe key aspects and trends if that is what is essential;
    • Individual data points:
      • place in a table or list if the individual data points are important.

Note - added bonus: Long descriptions assist all potential users to extract the essential information - they help you explain your intention for including the image.

The descriptions will also be indexed by search engines making your information more discoverable.

Longdesc code example

<img src="graph.gif" alt="graph of sales 2004/5" longdesc="graph.html">

A complicated graph with two data lines showing sales over 12 months - requires long description  2 different decriptions for the same graph. First details the trends, second details all data points - choice is dependent on the reason for the graph. Both pages are correctly formatted HTML with a return link.