EPUB 3 Accessibility Guidelines

Images

Images that are central to the understanding of a publication must always include a text alternative in their alt attribute.

In the case of complex images, a detailed description should also be added. Although the aria-describedby attribute can be used to link an image to a description in the same file, no mechanism currently exists to link to an out-of-band description. Work is ongoing to remedy this problem.

If the image is purely decorative, the alt attribute should be left empty. For improved, accessibility, an ARIA role attribute with the property presentation should also be attached.

Note

If an image is important to the publication, but not required to be read at the point of insertion (i.e., it is not part of the logical reading order), use a figure tag to enclose it.

Note

The details element has been removed from HTML5, but remains under development for HTML 5.1. As use of the element cannot be guaranteed to pass future updates to epubcheck, it is not recommended for describing content at this time.

Examples

Example 1 — Significant simple image (no description required)
<img
     src="covers/9781449328030_lrg.jpg"
     alt="First Edition" />
Example 2 — Significant complex image (description required)
<figure>
   <img
        src="graphics/water-cycle.jpg"
        aria-describedby="water-cycle-desc"
        alt="The hydrologic cycle, showing the 
          circular nature of the process as water 
          evaporates from a body of water and 
          eventually returns to it"/>
   <figcaption>
      The hydrologic cycle
      <aside class="hidden" id="water-cycle-desc">
         <p>
            The diagram shows the processes of 
            evaporation, condensation, 
            evapotranspiration, water storage 
            in ice and snow, and precipitation. 
            A large body of water …
         </p>
      </aside>
   </figcaption>
</figure>
Example 3 — Decorative image
<img
     src="graphics/gothic-border.png"
     role="presentation"
     alt=""/>

Compliance References and Standards

Additional Resources