EPUB Accessibility

Category:

Summary

The EPUB Accessibility specification defines discoverability requirements and accessibility conformance for EPUB publications.

Overview

As EPUB is built on Open Web Platform technologies like HTML and CSS, the EPUB Accessibility specification builds on the Web Content Accessibility Guidelines (WCAG) to define accessibility conformance for EPUB publications.

The primary advantage of this approach to accessibility is that it keeps EPUB aligned with the body of work that has already been done to make web content accessible. It also immediately makes web content accessibility specialists knowledgeable about the issues involved in ebook production. More generally, it means that content creators seeking to discover how to make their publications more accessible have a wealth of general resources available to them beyond this knowledge base.

But EPUB is also its own unique format, and WCAG is not a simple blanket set of practices that all apply in every situation. The knowledge base aims to bridge this gap for EPUB content by focusing on how to make rich publications that adhere to WCAG. Unlike the general web, where each site's design often brings its own unique issues, books are more often composed of the same sets of building blocks, making accessibility mappings useful to a broad range of publishers.

Conformance

The EPUB Accessibility specification defines two key areas for conformance:

1. Discoverability

The discovery section of the specification identifies schema.org accessibility metadata that publishers have to include in the EPUB package document.

It is required that all publications include the following:

A list of all accessibility features (accessibilityFeature).
The sufficient access modes that can be used to read the content, particularly those that only require a single capability (accessModeSufficient).
Any potential physical hazards the content might present (accessibilityHazard).

It is also recommended to provide a summary when the other metadata does not fully capture everything a user needs to know (accessibilitySummary). The modes in which the content is expressed (accessMode) should also be listed.

Note

Prior to EPUB Accessibility 1.2, the accessMode property was required and the accessModeSufficient property was recommended. Their priorities were switched because the sufficient access modes are more helpful to users when searching for content they can read.

A more complete overview of this metadata is provided in the Schema.org Metadata section of this knowledge base.

The inclusion of this metadata allows EPUB publications to be self-descriptive about their accessibility conformance, or lack thereof.

2. Content Accessibility

The accessibility section of the specification describes content conformance requirements. These requirements break down into two sections:

WCAG Conformance

EPUB publications must, at a minimum, meet WCAG 2.0 Level A in order to conform to the specification. It is recommended that publishers strive to meet the latest recommended version of WCAG 2 at level AA, however.

EPUB-specific Conformance

The specification defines two conformance criteria that are currently specific to EPUB: page navigation and synchronized media playback.

Meeting these requirements is not yet a firm requirement of the specification, however. The pagination requirements only apply when publishers can anticipate their publications will be used in mixed print-digital environments, and the synchronization requirements are optional to meet.

Reporting

The accessibility specification defines the following reporting metadata for EPUB publications:

What version of the specification and what WCAG level was met is listed using the dcterms:conformsTo property.
Who evaluated the publication is listed using the a11y:certifiedBy property.
What credentials the evaluator has, if any, is listed using the a11y:certifierCredential property.
Where to find a more in-depth evaluation report is listed using the a11y:certifierReport property.

A complete listing of this metadata and how to use it is provided in the Evaluation Metadata section of this knowledge base.

Accessibility Contact

The EPUB Accessibility specification also defines contact metadata (a11y:contactEmail) so that user's can report accessibility issues with an EPUB publication or ask additional questions about its conformance.

Optimizations

An informative section of the specification deals with "optimized publications". These are publications that do not meet the WCAG requirements for being widely accessible but that are optimized for users with specific needs.

An example of this type of publication is an audio book. Audio books are accessible for persons who are blind, for example, but not for the deaf. Optimized publications are expected to conform to a standard for their target audience, but the accessibility specification does not specify these standards (i.e., this conformance is outside the scope of the specification).

Although optimized publication cannot meet the requirements of the EPUB Accessibility specification, that is not meant to discourage their production. When publishers create these kinds of publications to another recognized standard, they can identify conformance to that standard instead.

Distribution

Another informative section of the specification deals with accessibility issues in distribution. Even though the publisher may do everything right in creating their content, issues in the distribution chain that limit the accessibility of the publication that users receive.

The most important of these issues is to not apply digital rights management schemes to a publication that limit access to the content. When this occurs, a perfectly accessible publication might no longer be readable at all if, for example, assistive technologies are prevented from reading out the text.

The other requirement is to provide accessibility metadata in whatever format a vendor uses to ingest the publication. It is common in trade publishing, for example, for ONIX records to be provided to distributors, which is also where they will harvest metadata about the publication. If the ONIX accessibility fields are not completed, users may lose the ability to search and discover the accessibility properties.

Techniques

The EPUB Accessibility was published together with a set of advisory techniques that explain how to meet its requirements.

These techniques do not delve into issues already covered by WCAG. Their focus is on explaining how to understand WCAG's requirements where they might be confusing when applied to EPUB publications.

Frequently Asked Questions

What tools are available to check conformance?

The DAISY Consortium maintains two tools to help check conformance of EPUB publications:

Ace: The Ace tool provides automated checking and reporting on a number of WCAG requirements. Passing the Ace validation tool is not sufficient to claim conformance to the specification, however, as not all WCAG requirements can be checked by machine.
SMART: The SMART tool is a complement to the Ace tool that helps evaluators walk through all the manual checks needed to ensure conformance to the accessibility specification.

Applies To

EPUB 3	EPUB 2	Audiobooks
Yes	Yes	No