Back to Error DirectoryW3C EPUBCheck Standard
RSC-030Critical Ingestion Error

File URLs are not allowed in EPUB, but found "resource".

File URLs are not allowed in EPUB, but found "resource".

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Fix all RSC-030 errors in your EPUB automatically

PreFlight checks for RSC-030 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 File URLs are not allowed in EPUB, but found "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 RSC-030: File URLs are not allowed in EPUB, but found "resource".

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule RSC-030 in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the RSC-030 specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.