Back to Error DirectoryW3C EPUBCheck Standard
HTM-011_SUGCritical Ingestion Error

Define the entity or use the numbered entity instead.

Define the entity or use the numbered entity instead.

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Fix all HTM-011_SUG errors in your EPUB automatically

PreFlight checks for HTM-011_SUG 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 Define the entity or use the numbered entity instead.. 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-011_SUG: Define the entity or use the numbered entity instead.

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule HTM-011_SUG in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the HTM-011_SUG specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.