Back to Error DirectoryW3C EPUBCheck Standard
HTM-044Critical Ingestion Error

Namespace uri "resource" was included but not used.

Namespace uri "resource" was included but not used.

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Fix all HTM-044 errors in your EPUB automatically

PreFlight checks for HTM-044 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 Namespace uri "resource" was included but not 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 HTM-044: Namespace uri "resource" was included but not used.

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule HTM-044 in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the HTM-044 specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.