RSC-030 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.

EPUBCheck · Resources and references

`RSC-030`

Updated: Nov 3, 2026

EPUBCheck RSC-030 is an error message: “File URLs are not allowed in EPUB, but found "…".” A file: URL points to a file on someone's computer; EPUB does not allow file URLs.

The official message

File URLs are not allowed in EPUB, but found "%1$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

Links or images that still point to the author's disk, such as file:///C:/Users/… after export.

How to fix it

Add the resource to the EPUB and reference it by a relative path, or remove the reference.

Terms used here

Other RSC messages

RSC-029 Data URL is not allowed in this context.
RSC-031 Remote resource references should use HTTPS, but found "…".
RSC-028 XML documents must be encoded in UTF-8, but … was detected.
RSC-032 Fallback must be provided for foreign resources, but found none for resource "…" of type "…".
RSC-027 XML document is encoded in UTF-16. It should be encoded in UTF-8 instead.
RSC-033 Relative URL strings must not have a query component, but found one in "…".

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