5.2.2. Enter the alt attribute for informative images

Sometimes, the image conveys a wealth of information that it is not possible to describe in simple text, just with the alt attribute (diagrams, complex graphs, etc.).

In this situation, it is an accessibility best practice to:

• Enter a short alternate text in the alt attribute that describes the basic purpose of the image.
• Plan for a content zone in which you can provide a detailed description of the image. Preferably, enter the detailed description either directly underneath the image or via a link to another page. For charts or complicated diagrams, the most appropriate detailed description is often a table of values, or a list.
• Indicate in the alternate text of the image how to access the more detailed description.

For example, in the case of a world map that shows the different countries in which a brand is present:

<img src="images/brand-map.png" alt="List of countries in which the Spartacus brand is present (detailed description available by clicking on the link underneath)" />
 
<a href="/zones-of-presence/">See the list of countries in which the Spartacus brand is present</a>

In some guidelines, it is recommended using the longdesc attribute for the link to the detailed description of the image. However, the use of this attribute does not guarantee access to the information for everyone, unlike the inclusion of a hard-coded link on the page. The use of the technique above is therefore preferable.