Back to Error DirectoryW3C EPUBCheck Standard
OPF-015Critical Ingestion Error

The property "resource" should not be declared in the OPF file.

The property "resource" should not be declared in the OPF file.

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PreFlight checks for OPF-015 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 property "resource" should not be declared 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-015: The property "resource" should not be declared in the OPF file.

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule OPF-015 in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the OPF-015 specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.