Introduction to Accessibility Metadata for Ebooks

Accessibility metadata should be included with every ebook, as it lets the reader know about what accessibility features have been included! This introduction discusses the importance of accessibility metadata, and shares examples of each type.

  • Subject(s):


  • Resource Type(s):

    Standards and Best Practices

  • Audience:


Suggested Prerequisite

Before you read this, you might want to read:

Accessibility Metadata

There is a lot of talk about accessibility metadata these days! You probably know it is highly recommended, really useful, and important to include in every ebook. But what is less well known is the most important stuff – like what it is, how to create it, and where to include it. This page should help clarify all of these key questions, or at least set you on the right path.

Accessibility metadata is metadata that shares the accessibility features in a book. When it is included in an ebook, it enables potential readers to know if the book meets their needs, and tells them all about the amazing accessibility features you have been working so hard to include. Accessibility metadata should always be included in an ebook’s OPF file, and creating and including ONIX records with accessibility metadata is highly recommended.

Accessibility metadata allows you to share all kinds of details about the book, like if you have included accessibility features such as page navigation or image descriptions, if the display is customizable, if there are any hazards (like sound or flashing) which could cause a physical reaction, and much more! Including as much accessibility metadata as possible will ensure that readers can be confident that they are picking a book that meets their needs.

There are three types of accessibility metadata which should be included with an EPUB.

Head on down to the Related Content section below to visit an in-depth overview of each type! But first, we’ll look at a few examples:

Examples Accessibility Metadata

This is an example of some accessibility metadata that comes from the “CreativeWork” Class, which is used for books (and movies, photographs, software programs, etc.). This metadata is included in an ebook’s OPF file. 

Code Test 1: CodeMirror

<meta property="schema:accessMode">textual</meta>
<meta property="schema:accessMode">visual</meta>
<meta property="schema:accessModeSufficient">textual,visual</meta>
<meta property="schema:accessModeSufficient">textual</meta>
<meta property="schema:accessibilityFeature">alternativeText</meta>
<meta property="schema:accessibilityFeature">structuralNavigation</meta>
<meta property="schema:accessibilityFeature">MathML</meta>
<meta property="schema:accessibilityHazard">noSoundHazard</meta>
<meta property="schema:accessibilityHazard">noFlashingHazard</meta>
<meta property="schema:accessibilityHazard">noMotionSimulationHazard</meta>
<meta property="schema:accessibilitySummary">This publication has no major violations in the ACE by Daisy App, and conforms to WCAG 2.0. Images are described, and there are several levels of navigation. It is not known to contain any element that may cause seizures or other physical reactions.</meta>

ONIX Record Accessibility Metadata

This is an example of some ONIX accessibility metadata for “Product Form Feature Type: E-publication accessibility detail”. The text wrapped in “<!-- …-->”, like <!--No reading system accessibility options disabled--> are human-readable comments that describe the “ProductFormFeatureValue” under each “ProductFormFeatureType”. The ONIX record is a separate XML file that is sometimes packaged with an ebook, and sometimes kept separate.

Note that this is just an example, so you have an idea of what it looks like. For an exhaustive list, check out Related Content below.

<!--No reading system accessibility options disabled-->
<!--Table of contents navigation-->
<!--Reading order-->
<!--Short alternative descriptions-->
<!--Language tagging provided-->

Conformance/Evaluation Metadata

Last but not least, there is conformance and evaluation metadata – this set of metadata should only be included once a publisher/book has been certified. When it is applicable, this metadata is included in an ebook’s OPF file. 

<link rel="dcterms:conformsTo" href=""/>
<meta property="a11y:certifiedBy">Accessibility Certifying Body</meta>
<meta property="a11y:certifierCredential">Credential that Establishes authority of certifying body</meta>
<link rel="a11y:certifierReport" href="https://linkToCertificationReport.html"/>

Next Steps


Understanding and Creating Metadata for Ebooks

Introduction to Accessibility Metadata

This resource defines all of the accessibility metadata properties and provides guidance on what to include in your OPF file.

Subject(s): Metadata
Resource Type(s): Standards and Best Practices

Creating Accessibility Metadata for an ONIX Record

Introduction to ONIX Metadata for Ebooks (and the Supply Chain)

This resource discusses the importance of ONIX accessibility metadata, and shares an example of the accessibility section of an ONIX file.

Subject(s): Metadata
Resource Type(s): Foundations and Rationale, Standards and Best Practices

External Links to More Information

EPUB Accessibility 1.0

This specification discusses discovery and accessibility of EPUB publications. Discovery relates to accessibility metadata. Accessibility includes guidelines in WCAG 2.0 and some additional items on page navigation and media overlays. The specification also discusses how to indicate conformance, information about optimized publications for specific use cases such as audiobooks, and a short section on distribution considerations.

Metadata in Publishing -The Hidden Information Essential for Accessibility

This archived webinar from the DAISY Consortium on June 24, 2020 discusses metadata. and Dublin core metadata is included in the EPUB file itself; and the Onix and Marc21 standards provide the ability to have external metadata used alongside the EPUB and can be used to include accessibility information in book catalogs.

EPUB Semantics, ARIA Roles, & Metadata

This page has brief explanations of how to mark up several types of content including sections, headings, emphasis, figures, sidebars, and blockquotes among others. It also discusses ARIA roles for the included elements where applicable. The page ends with a discussion of accessibility metadata.

Accessible Publishing Knowledge Base

This is an excellent reference with details and best practices for many EPUB accessibility topics. It provides explanations and code examples. Coverage includes EPUB accessibility, validation, metadata, HTML, and CSS from the perspective of using available markup elements to their full potential for accessibility.

Balisage Paper: Accessibility Metadata Statements

This paper discusses the different fields available in the accessibility metadata available for an EPUB. It also has some resources for ONIX and MARC21 listed at the end.

EPUB Accessibility Using InDesign

This course on LinkedIn Learning by Laura Brady covers how to use InDesign to make ebooks that are as accessible as possible. Items covered include separating style and content, navigation and structure, and image descriptions. Page lists and the Ace Accessibility checker are also covered.

Display Techniques for EPUB Accessibility Metadata

This specification explains how to present the accessibility metadata in an EPUB file to end users. It covers several areas: screen reader friendly, full audio, accessibility summary, conformance, certification, hazards, and lists all available metadata.

Display Techniques for ONIX Accessibility Metadata

This page covers how to determine accessibility information based on the ONIX metadata. ONIX can be useful because it is available in a catalog before a user obtains the EPUB itself. Categories covered are: screen reader friendly, full audio, accessibility summary, conformance, certification, hazards, and listing all available accessibility metadata.

European Accessibility Act requirements: Are publishing standards as EPUB, ONIX and fully compliant?

This page discusses the European accessibility requirements set to come into effect in 2025. Research was done to discover whether the existing metadata schemes of ONIX and metadata provide the needed information about the accessibility of ebooks. The results suggest that these do provide what is needed. A more detailed report is also available for download.

Providing Accessibility Metadata in ONIX

This document gives an overview of the types of accessibility information that can be included in anONIX record. It includes specific accessibility features, and whether an ebook meets the EPUB accessibility specification.

Writing the AccessibilitySummary

The “accessibilitySummary” piece of metadata provides a human readable description of the accessibility of the an EPUB. This resource discusses how to write one that is useful for everyone – from readers, to libraries, to vendors, and more.

Content Source Acknowledgement