Back to Error DirectoryW3C EPUBCheck Standard
OPF-098Critical Ingestion Error

The "href" attribute must reference resources, not elements in the ...

The "href" attribute must reference resources, not elements in the package document, but found URL "resource".

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Fix all OPF-098 errors in your EPUB automatically

PreFlight checks for OPF-098 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 "href" attribute must reference resources, not elements in the package document, but found URL "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-098: The "href" attribute must reference resources, not elements in the package document, but found URL "resource".

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule OPF-098 in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the OPF-098 specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.