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EPUBCheck · Package document (OPF)

OPF-050

Updated:

EPUBCheck OPF-050 is an error message: “TOC attribute references resource with non-NCX mime type; "application/x-dtbncx+xml" is expected.” The spine's toc attribute points to an item that is not an NCX file.

The official message

TOC attribute references resource with non-NCX mime type; "application/x-dtbncx+xml" is expected.

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

Typical causes

How to fix it

  • Point toc at the NCX item (media type application/x-dtbncx+xml), or remove the attribute in an EPUB 3 without NCX.

Terms used here

Other OPF messages

  • OPF-049 Item id "…" was not found in the manifest.
  • OPF-048 Package tag is missing its required unique-identifier attribute and value.
  • OPF-053 Date value "…" does not follow recommended syntax as per http://www.w3.org/TR/NOTE-datetime:….
  • OPF-054 Date value "…" is not valid as per http://www.w3.org/TR/NOTE-datetime:….
  • OPF-043 Spine item with non-standard media-type "…" has no fallback.

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

FAQ

What does EPUBCheck OPF-050 mean?

EPUBCheck OPF-050 is an error message: “TOC attribute references resource with non-NCX mime type; "application/x-dtbncx+xml" is expected.” The spine's toc attribute points to an item that is not an NCX file.

Is OPF-050 an error?

OPF-050 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.