Back to Error DirectoryW3C EPUBCheck Standard
PKG-006Critical Ingestion Error

Mimetype file entry is missing or is not the first file in the arch...

Mimetype file entry is missing or is not the first file in the archive.

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Fix all PKG-006 errors in your EPUB automatically

PreFlight checks for PKG-006 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 Mimetype file entry is missing or is not the first file in the archive.. 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-006: Mimetype file entry is missing or is not the first file in the archive.

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule PKG-006 in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the PKG-006 specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.