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EPUB is an e-book format. An EPUB e-book can be downloaded and read on a device like a smartphone, tablet, computer, or e-reader. It is a free and open standard published by the International Digital Publishing Forum. The term is short for electronic publication and is sometimes styled ePub. EPUB became an official standard of the IDPF in September 2007, superseding the older Open eBook standard.[2] The Book Industry Study Group endorses EPUB 3 as the format of choice for packaging content and has stated that the global book publishing industry should rally around a single standard.[3] EPUB is the most widely supported vendor-independent XML-based (as opposed to PDF) e-book format; that is, it is supported by the largest number of hardware readers, including Amazon Kindle Fire.[4]

It is also widely used on many software readers such as iBooks on Apple devices, and Google Books on Android. iBooks also supports the proprietary iBook format. This format is based on the EPUB format but depends upon custom widget code in the iBooks app to function.[5]

EPUB 2.0 was approved in October 2007, with a maintenance update (2.0.1) approved in September 2010.[6] The EPUB3 specification was published in November 2014. New major features include support for precise layout or specialized formatting, such as for comic books,[7] and MathML support.

The format and many readers support the following:

An EPUB file is a ZIP archive that contains what is in effect an entire website including HTML files, images, CSS style sheets, and other assets. It also contains metadata. EPUB 3 is the latest version. By using HTML5 publications can contain video, audio, and interactivity, just like websites in modern browsers.[9]

An ePub publication is delivered as a single file. This file is an unencrypted zipped archive containing a set of interrelated resources.[13]

An OCF Abstract Container defines a file system model for the contents of the container. The file system model uses a single common root directory for all of the contents of the container. All (non-remote) resources for publications are in the directory tree headed by the container’s root directory, although no specific file system structure is mandated for this. The file system model includes a mandatory directory named META-INF that is a direct child of the container's root directory and is used to store the following special files:

The first file in the archive must be the mimetype file. It must be uncompressed so that non-ZIP utilities can read the mimetype. The mimetype file must be an ASCII file that contains the string application/epub+zip. It must be unencrypted, and the first file in the ZIP archive. This file provides a more reliable way for applications to identify the mimetype of the file than just the .epub extension.[13]

There must be a META-INF directory containing container.xml. This file points to the file defining the contents of the book, the OPF file, though additional alternative rootfile elements are allowed.[13] Apart from mimetype and META-INF/container.xml, the other files (OPF, NCX, XHTML, CSS and images files) are traditionally put in a directory named OEBPS. An example container.xml:

Content documents include:[15] HTML 5 content, navigation documents, SVG documents, scripted content documents, and fixed layout documents. Contents also include CSS and PLS documents. Navigation documents supersedes the NCX grammar used in EPUB 2.

Many editors exist including calibre, Sigil, Adobe InDesign, Genebook and LaTeX. An open source tool called epubcheck exists for validating and detecting errors in the structural markup (OPS, OPF, OCF) as well as the XHTML and image files. The tool can be run from the command line, or used in webapps and applications as a library and is also available on EPUB Validator.

Readers exist for all major hardware platforms including iBooks and Google Play Books.



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Us staff, “EPUB -,” Continuing Education on New Data Standards & Technologies, accessed July 17, 2019,