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EPUBCheck · Package and ZIP container

PKG-003

Updated:

EPUBCheck PKG-003 is an error message: “Unable to read EPUB file header. This is likely a corrupted EPUB file.” EPUBCheck could not read the start of the file as a ZIP archive, so it is not a usable EPUB.

The official message

Unable to read EPUB file header. This is likely a corrupted EPUB file.

Default severity
Error. The EPUB breaks a rule of the specification and is invalid. Stores and Send to Kindle may reject it, and EPUBCheck exits with status 1.
EPUBCheck version
5.4.0

Typical causes

  • The file is not really an EPUB: a PDF, MOBI or other file renamed to .epub.
  • The download or copy was cut short and the file is truncated.

How to fix it

  • Download or export the EPUB again and compare its size with the original.
  • Rename a copy to .zip and try to open it: if no ZIP tool can, the file has to be rebuilt from its source.

Terms used here

Other PKG messages

  • PKG-004 Corrupted EPUB ZIP header.
  • PKG-001 Validating the EPUB against version … but detected version ….
  • PKG-005 The mimetype file has an extra field of length …. The use of the extra field feature of the ZIP format is not permitted for the mimetype file.
  • PKG-006 Mimetype file entry is missing or is not the first file in the archive.
  • PKG-007 The content of the mimetype file must be the string "application/epub+zip"…
  • PKG-009 The file name "…" contains characters that are not allowed in OCF file names: ….

Message text and severity from EPUBCheck 5.4.0 (W3C, BSD-3-Clause). Explanation by EPUBLab.

FAQ

What does EPUBCheck PKG-003 mean?

EPUBCheck PKG-003 is an error message: “Unable to read EPUB file header. This is likely a corrupted EPUB file.” EPUBCheck could not read the start of the file as a ZIP archive, so it is not a usable EPUB.

Is PKG-003 an error?

PKG-003 is reported as error by default. The EPUB breaks a rule of the specification and is invalid. Stores and Send to Kindle may reject it, and EPUBCheck exits with status 1.