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EPUBCheck · Resources and references

RSC-028

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EPUBCheck RSC-028 is an error message: “XML documents must be encoded in UTF-8, but … was detected.” An XML file uses an encoding other than UTF-8, which EPUB requires for XML documents.

The official message

XML documents must be encoded in UTF-8, but %1$s was detected.

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

  • A file saved as ISO-8859-1, Windows-1252 or another legacy encoding, often declared in its XML declaration.

How to fix it

  • Convert the file to UTF-8 and change the XML declaration to encoding="UTF-8" (or remove the encoding attribute).

Terms used here

Other RSC messages

  • RSC-027 XML document is encoded in UTF-16. It should be encoded in UTF-8 instead.
  • RSC-029 Data URL is not allowed in this context.
  • RSC-026 URL "…" leaks outside the container (it is not a valid-relative-ocf-URL-with-fragment string)
  • RSC-030 File URLs are not allowed in EPUB, but found "…".
  • RSC-031 Remote resource references should use HTTPS, but found "…".
  • RSC-032 Fallback must be provided for foreign resources, but found none for resource "…" of type "…".

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

FAQ

What does EPUBCheck RSC-028 mean?

EPUBCheck RSC-028 is an error message: “XML documents must be encoded in UTF-8, but … was detected.” An XML file uses an encoding other than UTF-8, which EPUB requires for XML documents.

Is RSC-028 an error?

RSC-028 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.