DES 4.2 Specify full descriptions for informational images

Complex images such as charts, diagrams and graphs need more description than simple alternative text alone (see DES 4.1) can reasonably display.

  • Specify the inclusion of a longer description:
    • On the same page, near the image (recommended);
    • On a separate page, linked using:
      • A normal text link to the description (recommended),
      • Specify the developer uses longdesc to point to the url - screen readers can use this code to link to the description,
      • A '[d]' link placed after the image to point to the url (use a normal link though 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 informationThat 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.

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.  A complicated graph with two data lines showing sales over 12 months - requires long description