Back to Error DirectoryW3C EPUBCheck Standard
OPF-064Critical Ingestion Error

OPF declares type "resource", validating using profile "resource".

OPF declares type "resource", validating using profile "resource".

Automated 1-Click Fix Ready

Fix all OPF-064 errors in your EPUB automatically

PreFlight checks for OPF-064 issues in memory and provides 1-click remediation during client-side packaging.

Scan & Fix Now

What This Error Means in Plain English

EPUBCheck detected OPF declares type "resource", validating using profile "resource".. 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-064: OPF declares type "resource", validating using profile "resource".

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule OPF-064 in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the OPF-064 specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.