Back to Error DirectoryW3C EPUBCheck Standard
MED-012Retailer Warning

The "media-overlay" attribute does not match the ID of the Media Ov...

The "media-overlay" attribute does not match the ID of the Media Overlay that refers to this document.

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What This Error Means in Plain English

EPUBCheck detected The "media-overlay" attribute does not match the ID of the Media Overlay that refers to this document.. 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 MED-012: The "media-overlay" attribute does not match the ID of the Media Overlay that refers to this document.

Manual Fix Instructions (for Sigil / Calibre)

  1. Locate the file and line flagged under rule MED-012 in your EPUB editor (Sigil or Calibre).
  2. Apply the required syntax correction matching the MED-012 specification.
  3. Re-pack and validate with PreFlight EPUB to confirm zero residual errors.