EPUB

A successor to the Open eBook Publication Structure, EPUB 2.0 was approved in October 2007, with a maintenance update (2.0.1) approved in September 2010. The EPUB 3.0 specification became effective in October 2011, superseded by a minor maintenance update (3.0.1) in June 2014. New major features include support for precise layout or specialized formatting (Fixed Layout Documents), such as for comic books, and MathML support. The current version of EPUB is 3.2, effective May 8, 2019. The (text of) format specification underwent reorganization and clean-up; format supports remotely hosted resources and new font formats (WOFF 2.0 and SFNT) and uses more pure HTML and CSS. In May 2016 IDPF members approved World Wide Web Consortium (W3C) merger, "to fully align the publishing industry and core Web technology". Version 2.0.1 EPUB 2.0 was approved in October 2007, with a maintenance update (2.0.1) intended to clarify and correct errata in the specifications being approved in September 2010. • Open Packaging Format (OPF) 2.0.1, describes the structure of the .epub file in XML. • Open Container Format (OCF) 2.0.1, collects all files as a ZIP archive. EPUB internally uses XHTML or DTBook (an XML standard provided by the DAISY Consortium) to represent the text and structure of the content document, and a subset of CSS to provide layout and formatting. XML is used to create the document manifest, table of contents, and EPUB metadata. Finally, the files are bundled in a zip file as a packaging format. Open Publication Structure 2.0.1 An EPUB file uses XHTML 1.1 (or DTBook) to construct the content of a book as of version 2.0.1. This is different from previous versions (OEBPS 1.2 and earlier), which used a subset of XHTML. There are, however, a few restrictions on certain elements. The MIME type for XHTML documents in EPUB is application/xhtml+xml. The complete specification for NCX can be found in the Specifications for the Digital Talking Book. An example .ncx file: Pride and Prejudice Austen, Jane Chapter 1 Open Container Format 2.0.1 An EPUB file is a group of files that conform to the OPS/OPF standards and are wrapped in a ZIP file. The OCF specifies how to organize these files in the ZIP, and defines two additional files that must be included. The mimetype file must be a text document in ASCII that contains the string application/epub+zip. It must also be uncompressed, unencrypted, and the first file in the ZIP archive. This file provides a more reliable way for applications to identify the MIME type of the file than just the .epub extension. • EPUB Publications 3.0, which defines publication-level semantics and overarching conformance requirements for EPUB Publications • EPUB Content Documents 3.0, which defines profiles of XHTML, SVG and CSS for use in the context of EPUB Publications • EPUB Open Container Format (OCF) 3.0, 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, which defines a format and a processing model for synchronization of text and audio The EPUB 3.0 format was intended to address the following criticisms: • While good for text-centric books, EPUB was rather unsuitable for publications that require precise layout or specialized formatting, such as comic books. The lack of a standardized way to annotate EPUB books led to difficulty in sharing and transferring annotations and therefore limited the use scenarios of EPUB, particularly in educational settings, because it cannot provide a level of interactivity comparable to the web. On June 26, 2014, the IDPF published EPUB 3.0.1 as a final Recommended Specification. In November 2014, EPUB 3.0 was published by the ISO/IEC as ISO/IEC TS 30135 (parts 1–7). In January 2020, EPUB 3.0.1 was published by the ISO/IEC as ISO/IEC 23736 (parts 1–6). Version 3.2 EPUB 3.2 was announced in 2018, and the final specification was released in 2019. A notable change is the removal of a specialized subset of CSS, enabling the use of non-epub-prefixed properties. The references to HTML and SVG standards are also updated to "newest version available", as opposed to a fixed version in time. Version 3.3 The W3C announced version 3.3 on May 25, 2023. Changes included stricter security and privacy standards; and the adoption of the WebP and Opus media formats. ==Features==

The format and many readers support the following: • Reflowable document: optimize text for a particular display • Fixed-layout content: pre-paginated content can be useful for certain kinds of highly designed content, such as illustrated books intended only for larger screens, such as tablets. • Like an HTML web site, the format supports inline raster and vector images, metadata, and CSS styling. • Page bookmarking • Passage highlighting and notes • A library that stores books and can be searched • Re-sizable fonts, and changeable text and background colors • Support for a subset of MathML • Better analytical support with compatible platforms • Digital rights management—can contain digital rights management (DRM) as an optional layer Digital rights management An EPUB file can optionally contain DRM as an additional layer, but it is not required by the specifications. DRMed EPUB files must contain a file called rights.xml within the META-INF directory at the root level of the ZIP container. == Adoption ==

EPUB is a popular format for electronic data interchange as it is based on HTML and other published standards and requires no licensing to implement. EPUB is widely supported by software readers such as Google Play Books on Android and Apple Books on iOS and macOS and hardware such as Amazon's Kindle e-readers. The EPUB format is the underlying framework for Apple's proprietary iBook format, which depends upon code from the Apple Books app to function. In 2022, Amazon's Send to Kindle service removed support for its own Kindle File Format in favor of EPUB. Popular EPUB producers of public domain and open licensed content include Project Gutenberg, Standard Ebooks, PubMed Central, SciELO and others. ==Security and privacy concerns==

EPUB requires readers to support the HTML5, JavaScript, CSS, SVG formats, making EPUB readers use the same technology as web browsers. Such formats are associated with various types of security issues and privacy-breaching behaviors e.g. Web beacons, CSRF, XSHM due to their complexity and flexibility. Such vulnerabilities can be used to implement web tracking and cross-device tracking on EPUB files. Security researchers also identified attacks leading to local files and other user data being uploaded. The "EPUB 3.1 Overview" document provides a security warning: ==Implementation==

An EPUB file is an archive that contains, in effect, a website. It includes HTML files, images, CSS style sheets, and other assets. It also contains metadata. EPUB 3.3 is the latest version. By using HTML5, publications can contain video, audio, and interactivity, just like websites in web browsers. An OCF (Open Container Format) 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 contents in the container. All (non-remote) resources for publications are in the directory tree headed by the container's root directory, though EPUB mandates no specific file system structure for this. The file system model includes a mandatory directory named META-INF that is a direct child of the container's root directory. META-INF stores container.xml. The first file in the archive must be the MIME type file. It must be unencrypted and uncompressed so that non-ZIP utilities can read the MIME type. The MIME type file must be an ASCII file that contains the string application/epub+zip. This file provides a more reliable way for applications to identify the MIME type of the file than just the .epub extension. • At least one content document. • One navigation document. • One package document listing all publication resources. This file should use the file extension .opf. It contains metadata, a manifest, fallback chains, bindings, and a spine. This is an ordered sequence of ID references defining the default reading order. The ePUB container may contain: • Style sheets • Pronunciation Lexicon Specification (PLS) documents • Media overlay documents Contents Content documents include HTML 5 content, navigation documents, SVG documents, scripted content documents, and fixed layout documents. Contents also include CSS and PLS documents. Navigation documents supersede the NCX grammar used in EPUB 2. Media overlays Books with synchronized audio narration are created in EPUB 3 by using media overlay documents to describe the timing for the pre-recorded audio narration and how it relates to the EPUB Content Document markup. The file format for Media Overlays is defined as a subset of SMIL. ==Software==

EPUB reader software exists for all major computing platforms, such as Adobe Digital Editions and calibre on desktop platforms, Google Play Books and Aldiko on Android and iOS, and Apple Books on macOS and iOS. There is also cross-platform editor software for creating EPUB files, including the open source programs calibre and Sigil. Most modern web browsers also support EPUB reader plugins. The Microsoft Edge browser had EPUB reader capability built in until September 2019. Reading software The following software can read and display EPUB files. Creation software The following software can create EPUB files. ==Notes==