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EPUBCheck · XHTML content documents

HTM-025

Updated:

EPUBCheck HTM-025 is a warning message: “Non-registered URI scheme type found in href.” A link uses a URI scheme that is not registered.

The official message

Non-registered URI scheme type found in href.

Default severity
Warning. The EPUB is still valid, but something is likely to cause problems in some reading apps. EPUBCheck exits with 0 unless you pass --failonwarnings.
EPUBCheck version
5.4.0

Typical causes

  • A typo in the scheme, or an app-specific scheme.

How to fix it

  • Correct the scheme to http, https, mailto or another standard one, or remove the link.

Terms used here

Other HTM messages

  • HTM-011 Entity is undeclared.
  • HTM-010 Namespace "…" is unusual for the prefix "epub".
  • HTM-009 The DOCTYPE provided is obsolete or irregular and can be removed.
  • HTM-045 Encountered empty href.
  • HTM-004 Irregular DOCTYPE: found "…", expected "…".
  • HTM-046 Fixed layout document has no "viewport" meta element.

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

FAQ

What does EPUBCheck HTM-025 mean?

EPUBCheck HTM-025 is a warning message: “Non-registered URI scheme type found in href.” A link uses a URI scheme that is not registered.

Is HTM-025 an error?

HTM-025 is reported as warning by default. The EPUB is still valid, but something is likely to cause problems in some reading apps. EPUBCheck exits with 0 unless you pass --failonwarnings.