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PKG-023Critical Ingestion Error

Validating the EPUB against version 2.0, default validation profile...

Validating the EPUB against version 2.0, default validation profile will be used.

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Fix all PKG-023 errors in your EPUB automatically

PreFlight checks for PKG-023 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 Validating the EPUB against version 2.0, default validation profile will be used.. 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-023: Validating the EPUB against version 2.0, default validation profile will be used.

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule PKG-023 in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the PKG-023 specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.