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EPUBCheck · NCX (EPUB 2 table of contents)

NCX-001

Updated:

EPUBCheck NCX-001 is an error message: “NCX identifier ("…") does not match OPF identifier ("…").” The NCX's dtb:uid does not match the package's unique identifier.

The official message

NCX identifier ("%1$s") does not match OPF identifier ("%2$s").

Default severity
Error. The EPUB breaks a rule of the specification and is invalid. Stores and Send to Kindle may reject it, and EPUBCheck exits with status 1.
EPUBCheck version
5.4.0

%1$s, %2$s… are filled in with the file, value or element EPUBCheck found.

Typical causes

How to fix it

  • Copy the value of the dc:identifier named by unique-identifier into the NCX meta name="dtb:uid".

Terms used here

Other NCX messages

  • NCX-004 NCX identifier ("dtb:uid" metadata) should not contain leading or trailing whitespace.
  • NCX-006 Empty "text" label in the NCX document

Message text and severity from EPUBCheck 5.4.0 (W3C, BSD-3-Clause). Explanation by EPUBLab.

FAQ

What does EPUBCheck NCX-001 mean?

EPUBCheck NCX-001 is an error message: “NCX identifier ("…") does not match OPF identifier ("…").” The NCX's dtb:uid does not match the package's unique identifier.

Is NCX-001 an error?

NCX-001 is reported as error by default. The EPUB breaks a rule of the specification and is invalid. Stores and Send to Kindle may reject it, and EPUBCheck exits with status 1.