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EPUBCheck · Resources and references

RSC-026

Updated:

EPUBCheck RSC-026 is an error message: “URL "…" leaks outside the container (it is not a valid-relative-ocf-URL-with-fragment string).” A relative URL climbs above the root of the EPUB (too many ../), pointing outside the container.

The official message

URL "%1$s" leaks outside the container (it is not a valid-relative-ocf-URL-with-fragment string)

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 path written for the original folder structure that has one ../ too many.

How to fix it

  • Count the folders between the document and the target and correct the relative path so it stays inside the book.

Terms used here

Other RSC messages

  • RSC-027 XML document is encoded in UTF-16. It should be encoded in UTF-8 instead.
  • RSC-028 XML documents must be encoded in UTF-8, but … was detected.
  • RSC-029 Data URL is not allowed in this context.
  • RSC-030 File URLs are not allowed in EPUB, but found "…".
  • RSC-031 Remote resource references should use HTTPS, but found "…".
  • RSC-020 "…" is not a valid URL (…)

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

FAQ

What does EPUBCheck RSC-026 mean?

EPUBCheck RSC-026 is an error message: “URL "…" leaks outside the container (it is not a valid-relative-ocf-URL-with-fragment string).” A relative URL climbs above the root of the EPUB (too many ../), pointing outside the container.

Is RSC-026 an error?

RSC-026 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.