[6] The EPUB 3.0 specification became effective in October 2011, superseded by a minor maintenance update (3.0.1) in June 2014.

[6] EPUB version 2.0.1 consists of three specifications: 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.

An EPUB file uses XHTML 1.1 (or DTBook) to construct the content of a book as of version 2.0.1.

Font-embedding can be accomplished using the @font-face property, as well as including the font file in the OPF's manifest (see below).

[15][b] EPUB also requires that PNG, JPEG, GIF, and SVG images be supported using the mimetypes image/png, image/jpeg, image/gif, image/svg+xml.

[15] An example skeleton of an XHTML file for EPUB looks like this: The OPF specification's purpose is to "[define] the mechanism by which the various components of an OPS publication are tied together and provides additional structure and semantics to the electronic publication".

Each file is represented by an item element, and has the attributes id, href, media-type.

All XHTML (content documents), stylesheets, images or other media, embedded fonts, and the NCX file should be listed here.

[16] The spine element lists all the XHTML content documents in their linear reading order.

The toc attribute of spine must contain the id of the NCX file listed in the manifest.

Files referenced in href must be listed in the manifest, and are allowed to have an element identifier (e.g. #figures in the example).

Of note here is that the values for the docTitle, docAuthor, and meta name="dtb:uid" elements should match their analogs in the OPF file.

[27] A notable change is the removal of a specialized subset of CSS, enabling the use of non-epub-prefixed properties.

[29] Changes included stricter security and privacy standards; and the adoption of the WebP and Opus media formats.

[30] The format and many readers support the following: An EPUB file can optionally contain DRM as an additional layer, but it is not required by the specifications.

This could affect the level of support for various DRM systems on devices and the portability of purchased e-books.

Popular EPUB producers of public domain and open licensed content include Project Gutenberg, Standard Ebooks, PubMed Central, SciELO and others.

[45][46][47] Security researchers also identified attacks leading to local files and other user data being uploaded.

For example, typical same-origin policies are not applicable to content that has been downloaded to a user's local system.

It includes HTML files, images, CSS style sheets, and other assets.

By using HTML5, publications can contain video, audio, and interactivity, just like websites in web browsers.

This file is an unencrypted zipped archive containing a set of interrelated resources.

The file system model uses a single common root directory for all contents in the container.

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.

[54] 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.