Accessibility tree

When users navigate a web document using an assistive technology they are not moving over exactly the same structure used to render the document in a browser. The browser instead generates a slightly different representation of the content called the accessibility tree and this is what it exposes to assistive technologies.

The accessibility tree is similar to the HTML DOM, but it includes additional information such as accessible names and descriptions. When interactive content takes advantage of ARIA roles, states and properties, the browser can ensure that the accessibility tree is kept up to date with changes.


Ace is an accessibility checking tool for EPUB publications developed by the DAISY Consortium.

Ace checks publications for common WCAG violations that can be detected by machine and generates a report on its discoveries.

More information about the tool is available from the Ace web site.


The Accessible Rich Internet Applications (ARIA) specification addresses the problem of making modern script-heavy web applications accessible for users of assistive technologies. These applications often do not use the built-in HTML elements, like buttons, in their interfaces, but turn otherwise static content, like images, into objects that users can click on to perform actions. While this is often done to make the interfaces more visually appealing, prior to ARIA the scripting necessary to make these features work were not reflected to users of assistive technologies. The result was to make such interfaces impossible to use.

ARIA addresses this problem by defining roles, states and properties so that the static elements can be presented in the accessibility tree like their more natural counterparts (e.g., a role of button can be assigned to an image so that assistive technologies can make it interactive).

Refer to the ARIA specification for more information.

Assistive Technology

An assistive technology (AT) is a device or software program capable of rendering content in ways that facilitate reading by persons with disabilities.

An assistive technology may be fully integrated into a reading system (iBooks with VoiceOver) or may work in conjunction with hardware and software to provide a reading experience better tailored to the reader's preferred modality (e.g., screen-reading software like JAWS and NVDA, content zooming technologies and refreshable braille displays).


The person or organization directly responsible for creating a digital publication and ensuring the quality and accessibility of the final product.

In the context of digital publication specifications and documentation, the "author" does not refer to the person who wrote the publication. It is commonly used to avoid personal pronouns (specifically "you"), as personal pronouns make translation to other languages more complex.