Give complex images a longer description

Sometimes it is not possible to fully describe an image in a short text alternative. For example, when it comes to an extensive infographic or a graph. These types of complex images should also be fully described in a text alternative. In that case, in addition to a concise description in the alt attribute, also provide a longer description in the surrounding text.

A longer description may also be placed on a separate page. In that case, place a link with the reference to that other page immediately before or after the image.

The surrounding text should also be linked to the image. This is not mandatory, but very useful. It can be done with the aria-describedby attribute. Use the ID of the element where the complex image is described. This information should also be visible to the visitors who are able see.