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Glossary

What is EPUBCheck?

Updated:

EPUBCheck is the official, open-source validator for EPUB files, maintained by the W3C and released under the BSD-3-Clause licence. It reports every problem as a message with a code such as RSC-005 and a severity: fatal, error, warning, info or usage.

Why it matters when you convert a PDF to EPUB

A valid EPUB is the best guarantee that a converted book opens everywhere, including stores and Send to Kindle. EpubCC validates the EPUBs of its public benchmark with EPUBCheck 5.4.0 and publishes the result, and our EPUBCheck reference explains every message.

EPUBCheck's exit code is 1 when it finds errors and 0 otherwise; --failonwarnings makes warnings fail too. Usage messages are off by default and appear with -u (--usage).

How EpubCC handles it: the EPUBs of the public benchmark were validated with EPUBCheck 5.4.0 and the results are published there; running EPUBCheck automatically after every conversion on the website is not built yet. The engine writes the parts EPUBCheck checks most often, such as the mimetype file, the manifest and the required metadata, the same way for every book.

Related terms

EPUBCheck messages about this

  • RSC-005 Error while parsing file: …
  • OPF-014 The property "…" should be declared in the OPF file.
  • PKG-018 The EPUB file could not be found.
  • INF-001 Rule … is under review and its severity may change in a future release. See the discussion at …
  • CHK-001 The custom message overrides file was not found.
  • CHK-008 Error encountered while processing an item "…"; skip other checks for the item.

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FAQ

What is EPUBCheck?

EPUBCheck is the official, open-source validator for EPUB files, maintained by the W3C and released under the BSD-3-Clause licence. It reports every problem as a message with a code such as RSC-005 and a severity: fatal, error, warning, info or usage.