The EPUB specification is a distribution and interchange format standard for digital publications and documents. EPUB defines a means of representing, packaging and encoding structured and semantically enhanced Web content, including HTML5, CSS, SVG and other resources, for distribution in a single-file format. EPUB is the industry standard for digital publications and is based on open technologies used on the Open Web Platform.
EPUB offers the greatest opportunity for mainstream accessibility requirements—i.e. it delivers the possibility of offering ebooks to print impaired readers at the same time, in the same format and at the same price as everyone else.
DAISY has been involved in the standardization of EPUB since its inception—first at the International Digital Publishing Forum (IDPF), and now within the World Wide Web Consortium (W3C). Thanks in part to our ongoing participation, accessibility has always been a first-class requirement throughout the EPUB standardization process.
Who is it for?
EPUB can be used by anyone who is creating digital content, be they from a large international publishing house or a self publisher working on their own. There is an enormous amount of resource available to help those who may not have the internal infrastructure to cope with an EPUB workflow
The EPUB standard is managed and maintained by Publishing@W3C. EPUB 3.2 is the latest version of the standard and offers the greatest opportunity for accessibility. W3C has published a list of changes relevant to this version.
The EPUB 3 standard is modular in nature, with core features and functionality defined across a family of sub-specifications.
The other specifications that comprise EPUB 3 are as follows:
- EPUB Packages [Packages32] — defines requirements for each Rendition of the content.
- EPUB Content Documents [ContentDocs32] — defines profiles of XHTML, SVG and CSS for use in the context of EPUB Publications.
- EPUB Media Overlays [MediaOverlays32] — defines a format and a processing model for synchronization of text and audio.
- EPUB Open Container Format (OCF) [OCF32] — defines a file format and processing model for encapsulating a set of related resources into a single-file (ZIP) EPUB Container.
- EPUB Accessibility [EPUBAccessibility] — defines accessibility conformance and discovery requirements for EPUB Publications.
These specifications represent the formal list recognized as belonging to EPUB 3, and that contain functionality referenced as part of the standard. New functionality is also added periodically through the development of extension specifications. Features and functionality defined outside of core revisions to the standard, while not formally recognized in this specification, are nonetheless available for use by Authors and Reading System developers.
EPUB has various profiles available within the standard and these include:
- EPUB Accessibility 1.0—for use with either EPUB 2 or EPUB 3 this profile sets the standard for enabling accessibility within mainstream EPUB products
- EPUB for Education—a version of EPUB 3 which focuses on the requirements of the education sector
EPUB files can be read on most ereader devices with a host of accessibility features. They are constructed using ordinary HTML5 and CSS (cascading style sheets) and offer a range of features that improve navigation and accessibility, such as:
- detailed structural markup
- ability to include prerecorded speech synchronised with the text (called ‘media overlays).
- accessible video,
- mathematical and technical content (via MathML)