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EPUBCheck · Package document (OPF)

OPF-048

Updated:

EPUBCheck OPF-048 is an error message: “Package tag is missing its required unique-identifier attribute and value.” The package element has no unique-identifier attribute, which is required.

The official message

Package tag is missing its required unique-identifier attribute and value.

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

  • Add unique-identifier with the id of the book's main dc:identifier, for example <package version="3.0" unique-identifier="uid">.

Terms used here

Other OPF messages

  • OPF-049 Item id "…" was not found in the manifest.
  • OPF-050 TOC attribute references resource with non-NCX mime type; "application/x-dtbncx+xml" is expected.
  • OPF-043 Spine item with non-standard media-type "…" has no fallback.
  • 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:….

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

FAQ

What does EPUBCheck OPF-048 mean?

EPUBCheck OPF-048 is an error message: “Package tag is missing its required unique-identifier attribute and value.” The package element has no unique-identifier attribute, which is required.

Is OPF-048 an error?

OPF-048 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.