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, images, and other resources — for distribution in a single-file format.

EPUB 3, the third major release of the standard, consists of a set of four specifications, each defining an important component of an overall EPUB Publication:

-EPUB Publications 3.0 [Publications30], which defines publication-level semantics and overarching conformance requirements for EPUB Publications.

-EPUB Content Documents 3.0 [ContentDocs30], which defines profiles of XHTML, SVG and CSS for use in the context of EPUB Publications.

-EPUB Open Container Format (OCF) 3.0 [OCF3], which defines a file format and processing model for encapsulating a set of related resources into a single-file (ZIP) EPUB Container.

-EPUB Media Overlays 3.0 [MediaOverlays30], which defines a format and a processing model for synchronization of text and audio.

EPUB has been widely adopted as the format for digital books (eBooks), and these new specifications significantly increase the format's capabilities in order to better support a wider range of publication requirements, including complex layouts, rich media and interactivity, and global typography features. The expectation is that EPUB 3 will be utilized for a broad range of content, including books, magazines
and educational, professional and scientific publications.

This document provides a starting point for content authors and software developers wishing to
understand these specifications. It consists of non-normative overview material, including a roadmap to
the four building-block specification documents that compose EPUB 3.

Another non-normative document, EPUB 3 Changes from EPUB 2.0.1 [EPUB3Changes], describes
changes in EPUB 3 from the previous version, but is intended primarily for Authors and EPUB Reading
System vendors migrating from EPUB 2.0.1 to EPUB 3 and for those who anticipate supporting both versions.