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PKG-005Critical Ingestion Error

The mimetype file has an extra field of length resource. The use of...

The mimetype file has an extra field of length resource. The use of the extra field feature of the ZIP format is not permitted for the mimetype file.

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Fix all PKG-005 errors in your EPUB automatically

PreFlight checks for PKG-005 issues in memory and provides 1-click remediation during client-side packaging.

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What This Error Means in Plain English

EPUBCheck detected The mimetype file has an extra field of length resource. The use of the extra field feature of the ZIP format is not permitted for the mimetype file.. Digital reading systems and bookstores require standard conformance to ensure compatibility across all reading apps.

Why Retailers & EAA Regulations Block This File

Automated book distributors (Apple Books, Amazon KDP, Kobo, and IngramSpark) run strict EPUBCheck validation on ingest and reject non-compliant files.

Technical Specification: W3C EPUBCheck rule PKG-005: The mimetype file has an extra field of length resource. The use of the extra field feature of the ZIP format is not permitted for the mimetype file.

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule PKG-005 in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the PKG-005 specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.