Back to Error DirectoryW3C EPUBCheck Standard
OBS-001Retailer Warning

Usage of resource is outdated.

Usage of resource is outdated.

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PreFlight checks for OBS-001 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EPUBCheck detected Usage of resource is outdated.. 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Technical Specification: W3C EPUBCheck rule OBS-001: Usage of resource is outdated.

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule OBS-001 in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the OBS-001 specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.