Accessible ePub guide
Resources and tools to learn how to publish accessible ePubs
Introduction to accessible publishing
This guide serves as an introduction to accessible digital publishing using EPUBs. You will learn how to create a 'born-accessible' EPUB, how to adapt your content to accessible formats, the techniques and tools used to make EPUBs accessible, and innovations and new techniques to make Universal Design for Learning (UDL) digital textbooks.
What is an ePub?
An EPUB is an electronic publication, a file format that is the current industry standard in digital publishing. EPUBs are a standardized format that can support the digitization of traditional print books and make best use of the flexibility of digital screens to resize, reflow and enhance text and media rich content. EPUBs support both unprotected and digital rights management solutions to protect publisher material and lock content to specific platforms and ecosystems. The EPUB format is based on web technologies and can be described as a “web page in a package”, with specific metadata and structural information that describes how it should be organized.
To read more about the anatomy of an EPUB, click here.
EPUBs must be opened by an 'EPUB reader', a piece of software that can correctly display the contents of an EPUB on a screen. Different readers support the features defined in the EPUB standard (EPUB 3.2 published in May 2019) to varying degrees. In some cases, readers will only support the older EPUB 2.0 standard, while the newer readers may or may not support specific features like media overlays for synchronizing text and audio. Some modern browsers (Microsoft Edge) can also open unprotected EPUBs. With the merger of IDPF (International Digital Publishing Forum) into W3C (the web's governance community), a shift is taking place from EPUBs viewable in specialized reader software and devices to digital publishing on the web.
To learn more about EPUBs, access our list of links and resources.
To learn about the history of digital publishing, view the timeline.
Making ePubs accessible
Accessibility in the digital world applies to the process of ensuring technology products, devices and services are usable, accessible and comprehensible to all people regardless of disability. It addresses three concerns: how persons with disabilities access electronic information; how content designs and developers ensure web pages, publications and other forms of digital content function correctly with assistive devices and services; and how content and digitization can be made 'born accessible', that is, designed from the onset for all users including those with disabilities and involving persons with disabilities and OPDs (organizations of persons with disabilities).
To read more about accessibility, see the ABCs of digital accessibility page.
As EPUBs share many of the same accessibility requirements as the web, many of the same techniques (i.e., image descriptions) that apply to web accessibility can be used when authoring accessible EPUBs. Nevertheless, certain core differences that are unique to EPUB must be noted, which are outlined below. Familiarize yourself with these techniques to ensure you have the best results when creating accessible EPUBs.
Accessible books vs. UDL books
The Accessible Digital Textbooks initiative supports the production and development of accessible digital textbooks and UDL digital textbooks. Accessible digital books have features designed to make reading more inclusive for specific users, including compatibility with screen readers for people who are blind or have low vision and for users with dyslexia or with learning disabilities who benefit from read aloud text, and support for assistive devices like switch control for users with motor impairment. Accessible textbooks may also be authored in multiple versions to fulfil the requirements of specific user groups, with added sign language video for learners who are deaf or hard of hearing, or with simplified text for learners with intellectual disability.
UDL books differ from the accessible variety in that all features, all learning styles and all learners with and without disabilities are considered equally. They differ also in that they are digital, accessible and versatile, allowing users to customize and combine diverse features, such as narration, sign language, interactivity, the audio description of images and other functions to suit different preferences, learning styles or access needs. An added benefit is that UDL books require only one publication to be produced to service all learners. This form of production is still new, however, featuring innovative techniques.
Two ways of producing accessible digital textbooks are:
1. Creating separate publications that address the needs of distinct disability groups.
This approach follows existing standards, is best supported by screen readers and is more familiar to publishers.
2. Creating a single publication that addresses the needs of all learner groups and learning styles.
This involves using certain nonstandard techniques to produce content that features universal content adaptation and is visually appealing, accessible and interactive to engage all learning styles. Publishers are less familiar with this approach, but interest in it is growing.
Is your content re-flowable or fixed layout?
Perhaps the single most important question to ask when considering authoring an accessible publication is whether the content is best suited to a reflowable or fixed layout style:
1) Reflowable layout. Reflowable layout functions like a regular web page, where the text wraps according to the screen size whether it is displayed on a desktop computer or mobile device. It allows the reader to change the size of the text, alter the contrast and navigate easily with compatible screen reader technology.
Reflowable layout is best suited for mainly text-based content with minimal imagery.
2) Fixed layout. Fixed layout functions like a children's picture book or a magazine, where the layout remains fixed the way the designer intended regardless of screen size. Fixed layout is best suited for designed content, such as image or exercise rich textbooks, in which the design and layout aid in their comprehension.
Whenever possible, reflowable layout is a more flexible choice for accessible digital textbooks and is best for learners who are blind or have low vision.
Quick EPUB accessibility techniques
- Use reflowable layout for maximum compatibility with screen readers, magnifiers and navigation.
- Use UTF-8 to ensure the interoperability of characters.
- Use MathML to represent complex formulas for screen readers.
- Use semantic HTML whenever possible (to assist text-to-speech, use EPUB:type to add semantic information).
- Include appropriate metadata.
- Place all text in a logical reading order; don’t rely only on visual cues.
- Avoid text or tables embedded in an image (if unavoidable, include it in the image description).
- Always add alt text/image descriptions (images, charts, graphs, infographics, decorations).
- When developing interactive accessible activities, use ARIA techniques to add semantic meaning to custom elements.
- Use rich navigability (tables of contents, chapter titles, etc.).
- Use Real Audio Narration for early grade learners.
- Use accurate metadata (accessMode, accessibilityFeature).
- Include a glossary.
- Include sign language video where possible (synchronized or embedded).
- Where design is a requirement, ensure design elements, such as colour and imagery, are not required to understand the underlying content.
- W3C EPUB Specifications and Projects: http://www.idpf.org/EPUB/dir/.
- Web Content Accessibility Guidelines: https://www.w3.org/WAI/standards-guidelines/wcag/.
- Anatomy of an EPUB 3 file: https://www.edrlab.org/EPUB/anatomy-of-an-EPUB-3-file/.
The Future of EPUBs
In 2017, the IDPF merged with W3C. This signalled a shift in the era of EPUB-dominated digital publishing towards a web-focused approach, where the best of packaged books EPUBs and the flexibility of the web (browser-based solutions) can come together. This new paradigm is called portable web publications (PWP) or, in some cases, packaged web publications. The new format differs from EPUB in that it is immediately accessible in any browser and does not require a specialized EPUB 'reader' application to view.
To read more about the developments and progress of PWPs, go to https://www.w3.org/TR/pwp-ucr/.