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EPUBCheck · Resources and references

EPUBCheck RSC-029: data URL not allowed here

Updated:

EPUBCheck RSC-029 is an error message: “Data URL is not allowed in this context.” A data: URL (content embedded in the URL itself) is used where EPUB does not allow it. EPUB 3.3 restricts data URLs so that every document a reader can navigate to is a real file in the container.

The official message

Data URL is not allowed in this context.

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

  • A data: URL used as a link target or as a document reading apps would navigate to.
  • Content generated by a tool that inlines everything as data URLs.

How to fix it

  1. Find the data: URL named in the message.
  2. Save the embedded content as a file in the EPUB, add it to the manifest and reference it by path.
  3. Validate again.

When it's not this

A file: URL pointing to a local disk is a different error, RSC-030.

Terms used here

Other RSC messages

  • RSC-028 XML documents must be encoded in UTF-8, but … was detected.
  • RSC-030 File URLs are not allowed in EPUB, but found "…".
  • RSC-027 XML document is encoded in UTF-16. It should be encoded in UTF-8 instead.
  • RSC-031 Remote resource references should use HTTPS, but found "…".
  • RSC-026 URL "…" leaks outside the container (it is not a valid-relative-ocf-URL-with-fragment string)
  • RSC-032 Fallback must be provided for foreign resources, but found none for resource "…" of type "…".

Sources

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

FAQ

What does EPUBCheck RSC-029 mean?

EPUBCheck RSC-029 is an error message: “Data URL is not allowed in this context.” A data: URL (content embedded in the URL itself) is used where EPUB does not allow it. EPUB 3.3 restricts data URLs so that every document a reader can navigate to is a real file in the container.

Is RSC-029 an error?

RSC-029 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.