DES 4.2 Specify full descriptions for informational images
Recommendations
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 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.
- 'Trend in ...':
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.
Examples

