contentopf

Contentopf refers to the package document used by the Open Packaging Format in EPUB publications. In practice, the package document is usually named content.opf and is stored inside the EPUB archive, although the specification allows other file names. The package document serves as the central description of the publication, letting software assemble metadata, resources, and the reading order. It is typically referenced by the EPUB container's container.xml, which points to the full path of the package document.

A contentopf file is written as XML and consists of several sections. The metadata section stores bibliographic information such as title, language, identifier, and creators, typically using Dublin Core elements. The manifest lists all resources used by the publication—HTML content documents, images, stylesheets, fonts, and others—each item tagged with an id, href, and media-type; optional properties can indicate the role of the item (for example, cover image or navigation document). The spine defines the linear reading order by listing itemref elements that reference manifest items; a linear attribute can indicate whether an item is part of the primary flow. The guide, used in EPUB 2, offers fallbacks to navigation landmarks but is optional.

While contentopf is central to EPUB 2 and widely present in EPUB 3, some publishers use different file names such as package.opf. Validation tools like epubcheck verify conformance to the relevant EPUB version.