Back to Error DirectoryW3C EPUBCheck Standard
CHK-001Retailer Warning

The custom message overrides file was not found.

The custom message overrides file was not found.

Automated 1-Click Fix Ready

Fix all CHK-001 errors in your EPUB automatically

PreFlight checks for CHK-001 issues in memory and provides 1-click remediation during client-side packaging.

Scan & Fix Now

What This Error Means in Plain English

EPUBCheck detected The custom message overrides file was not found.. 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 CHK-001: The custom message overrides file was not found.

Manual Fix Instructions (for Sigil / Calibre)

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