EPUB 3 Accessibility Guidelines


There are many reasons why describing content adds to its accessibility for all readers. Although often considered only useful for non-visual readers, descriptions facilitate comprehension and provide context for readers with a wide range of needs. They can also assist readers whose first language may not be that of the text being read.


The aria-describedby attribute can be used to add a description to any HTML5 element, not just img. It is not well supported, however, and is not useful for complex image descriptions as the text it references is flattened to a simple text string.

Compliance References and Standards

Frequently Asked Questions

Why link to visible descriptions?

Even though a description is a visible part of the current page, linking to it provides a programmatic means for users of assistive technologies to rapidly access the description without having to hunt through the page content.

Why not longdesc?

The longdesc attribute is an HTML5 extension not currently supported by EPUB. It is also limited to being attached to img elements.

Why not aria-details?

The aria-details attribute is currently under development and not supported by assistive technologies. It will allow an association to be made with a description in a details element. Although similar to aria-describedby, the aria-details attribute will not result in stringified content (i.e., the user will be able to navigate the description as structured HTML).