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Glossary

What is the OPF package document?

Updated:

The OPF (Open Packaging Format) file, or package document, is the XML file that describes an EPUB: its metadata, the manifest of every file and the spine that sets the reading order. Reading apps find it through META-INF/container.xml.

Why it matters when you convert a PDF to EPUB

When a PDF becomes an EPUB, everything the converter recovers ends up declared here: the title and language taken from the PDF, each chapter file in reading order, the images and fonts, the cover and the navigation document. A mistake in the OPF affects the whole book, which is why OPF messages are the largest group in EPUBCheck.

How EpubCC handles it: the package document it writes declares version 3.0, a dc:identifier derived from the book's content (the same PDF gives the same identifier, so a reconversion does not show up as a new book), the title, the detected language, the author when the PDF metadata has one, and dcterms:modified set to the time of the conversion. The spine lists the chapters in reading order.

Related terms

EPUBCheck messages about this

  • OPF-003 Item "…" exists in the EPUB, but is not declared in the OPF manifest.
  • OPF-030 The unique-identifier "…" was not found.
  • PKG-020 OPF file "…" could not be found.
  • RSC-002 Required META-INF/container.xml resource could not be found.
  • RSC-003 No rootfile tag with media type "application/oebps-package+xml" was found in the container.
  • RSC-005 Error while parsing file: …
  • RSC-019 EPUBs with Multiple Renditions should contain a META-INF/metadata.xml file.
  • OPF-001 There was an error when parsing the EPUB version: ….
  • OPF-002 The OPF file "…" was not found in the EPUB.
  • OPF-004 Invalid prefix declaration: leading or trailing whitespace is not allowed.

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FAQ

What is the OPF package document?

The OPF (Open Packaging Format) file, or package document, is the XML file that describes an EPUB: its metadata, the manifest of every file and the spine that sets the reading order. Reading apps find it through META-INF/container.xml.