Provide long descriptions for complex images using longdesc
Make sure complex images are assigned longdesc attributes that lead to full text descriptions
Whenever a complex image is used in a page and the full text description of that image cannot be embedded in the ALT attribute value of the image or placed right next to it, another option is use the ALT attribute value to describe the image’s nature or purpose, and create an additional remote file, in which the long text description of the complex image can then be found.
To do so, simply use the LONGDESC attribute to reference a URI, which will be the address to this other adequately structured HTML resource. This additional page can either be seamlessly embedded in the website’s template, or act as a standalone resource. Regardless of whether it is embedded in the site overall design or not, this page should always provide a link back to the original page containing the complex image, so users can easily navigate back to where they came from. Note that in most cases however, the information provided through the LONGDESC attribute will only be available to screen reader users, so other options to handle [...]