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EPUBCheck · Package document (OPF)

OPF-092

Updated:

EPUBCheck OPF-092 is an error message: “Language tag "…" is not well-formed: ….” A language tag in the EPUB is not a well-formed BCP 47 tag.

The official message

Language tag "%1$s" is not well-formed: %2$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

  • Language names instead of codes, such as "English", or underscores, such as "en_US".

How to fix it

  • Use a BCP 47 code: en, en-US, es, pt-BR, ja, ar. The language drives hyphenation and text-to-speech in reading apps.

Terms used here

Other OPF messages

  • OPF-091 The item href URL must not have a fragment identifier.
  • OPF-093 The "media-type" attribute is required for linked resources located in the EPUB container
  • OPF-090 It is encouraged to use MIME media type "…" instead of "…".
  • OPF-088 Unrecognized epub:type value "…".
  • OPF-096 Non-linear content must be reachable, but found no hyperlink to "…".
  • OPF-097 Resource "…" is listed in the manifest, but no reference to it was found in content documents.

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

FAQ

What does EPUBCheck OPF-092 mean?

EPUBCheck OPF-092 is an error message: “Language tag "…" is not well-formed: ….” A language tag in the EPUB is not a well-formed BCP 47 tag.

Is OPF-092 an error?

OPF-092 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.