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Glossary

What is EPUBCheck?

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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. EPUBLab 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).

Related terms

EPUBCheck messages about this

  • RSC-005 Error while parsing file: …
  • OPF-014 The property "…" should be declared in the OPF file.
  • 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-002 Unrecognized custom message id … encountered in message overrides file "…".
  • CHK-003 Unrecognized custom message severity "…" encountered in message overrides file "…".
  • CHK-007 Error encountered while processing custom message file "…": "…".

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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.