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OPF-029Critical Ingestion Error

The file "resource" does not appear to match the media type resourc...

The file "resource" does not appear to match the media type resource, as specified in the OPF file.

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Fix all OPF-029 errors in your EPUB automatically

PreFlight checks for OPF-029 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 file "resource" does not appear to match the media type resource, as specified in the OPF 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 OPF-029: The file "resource" does not appear to match the media type resource, as specified in the OPF file.

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule OPF-029 in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the OPF-029 specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.