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Glossary

What is EPUB 2?

Updated:

EPUB 2 is the previous generation of the EPUB standard (2.0.1 dates from 2010), based on XHTML 1.1 and an NCX table of contents. It has been superseded by EPUB 3 but many older files still use it.

Why it matters when you convert a PDF to EPUB

There is no reason to produce EPUB 2 from a PDF today: current readers, Send to Kindle and Kobo all accept EPUB 3. EPUB 2 matters when you validate or repair older files, because EPUBCheck validates them against the EPUB 2 rules and reports messages that only apply there, such as NCX identifiers.

How EpubCC handles it: it never writes EPUB 2. Its output is EPUB 3 only, without an NCX, which current reading apps, Send to Kindle and Kobo devices accept. If you need to validate or fix an EPUB 2 file you already have, the EPUBCheck reference on this site explains the messages that only apply to EPUB 2, such as the NCX ones.

Related terms

EPUBCheck messages about this

  • NCX-001 NCX identifier ("…") does not match OPF identifier ("…").
  • NAV-001 The nav file is not supported for EPUB v2.
  • PKG-001 Validating the EPUB against version … but detected version ….
  • PKG-023 Validating the EPUB against version 2.0, default validation profile will be used.
  • OPF-031 File listed in reference element in guide was not declared in OPF manifest: ….
  • OPF-032 Guide references "…" which is not a valid "OPS Content Document".
  • OPF-037 Found deprecated media-type "…".
  • OPF-041 Fallback-style item with id "…" could not be found.
  • OPF-042 "…" is not a permissible spine media-type.
  • OPF-055 … tag is empty.

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FAQ

What is EPUB 2?

EPUB 2 is the previous generation of the EPUB standard (2.0.1 dates from 2010), based on XHTML 1.1 and an NCX table of contents. It has been superseded by EPUB 3 but many older files still use it.