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):


  • Resource Type(s):

    Foundations and Rationale, Standards and Best Practices

  • Audience:


Suggested Prerequisite

Before you read this, you might want to read:

You might know all about how to create and include accessibility metadata (if not, take a look in the Next Steps below), and feel like you have got accessibility metadata handled! But, there is more metadata that can be created and included with your ebook. This other type of metadata is called ONIX. 

ONIX Metadata

ONIX is an XML-based standard for rich book metadata, providing a consistent way for publishers, retailers and their supply chain partners to communicate a wide range of information about their products. It is a commercial data format, designed to be used globally, and not limited to any one language or the characteristics of a specific national book trade. It’s widely used throughout the book and e-book supply chain in North America, Europe and Australasia, and is increasingly being adopted in the Asia Pacific region and South America too.

An ONIX record is a separate XML file that is sometimes packaged together with an ebook, and sometimes left separate, but either way, it is distributed alongside an ebook. It contains all kinds of metadata about a book, like title, author, edition, page count, etc. And, as you may suspect since you are on the Accessible Publishing Learning Network, it also has a set of accessibility metadata. 

Here it is packaged together with other files that make up an EPUB:

The Importance of ONIX

ONIX records can be used to describe product features for the book supply chain, and can be sent from the publisher or creator of the EPUB file/digital book to those who will make the products available for sale, lending or subscription. 

It is estimated that making your digital content more accessible might increase the number of potential readers by 10 or 15%, so if you have gone to all the trouble of improving the accessibility of your titles, then you should use your metadata to highlight this!


This example shares the accessibility metadata section of an ONIX file. You’ll notice that the features are in pairs: ProductFormFeature, which always has a value of 09, and ProductFormFeatureValue, which varies. 

Feature type 09 simply means that the Feature value is taken from List 196, which lists the “E-publication Accessibility Details”. The numbers under ProductFormFeatureValue correspond to numbers on List 196. Let’s take a look at an example:

<?xml version="1.0" encoding="utf-8"?>
<ONIXMessage xmlns="" release="3.0">
<SenderName>Pretend Publisher</SenderName>

You can take a look at Code List 196 to learn what accessibility features the numbers 10, 11, and 13 (the values for “ProductFormFeatureValue” in each pair) correspond to!

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

External Links to More Information

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.

Display Techniques for ONIX 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.

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.

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.

Content Source Acknowledgement

EDItEUR: ONIX Overview

W3C: Display Techniques for ONIX Accessibility Metadata 1.0 –