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EPUBCheck · Resources and references

RSC-032

Updated:

EPUBCheck RSC-032 is an error message: “Fallback must be provided for foreign resources, but found none for resource "…" of type "…".” A resource in a format reading apps are not required to support (a foreign resource) is used without a fallback in a core format.

The official message

Fallback must be provided for foreign resources, but found none for resource "%1$s" of type "%2$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

  • Images in TIFF, BMP or another non-core format referenced directly from the content.

How to fix it

  • Convert the resource to a core media type (for images: JPEG, PNG, GIF, WebP or SVG).
  • Or provide a fallback: a manifest fallback attribute, or a picture or object element with an alternative.

Terms used here

Other RSC messages

  • RSC-031 Remote resource references should use HTTPS, but found "…".
  • RSC-033 Relative URL strings must not have a query component, but found one in "…".
  • RSC-030 File URLs are not allowed in EPUB, but found "…".
  • RSC-029 Data URL is not allowed in this context.
  • RSC-028 XML documents must be encoded in UTF-8, but … was detected.
  • RSC-027 XML document is encoded in UTF-16. It should be encoded in UTF-8 instead.

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

FAQ

What does EPUBCheck RSC-032 mean?

EPUBCheck RSC-032 is an error message: “Fallback must be provided for foreign resources, but found none for resource "…" of type "…".” A resource in a format reading apps are not required to support (a foreign resource) is used without a fallback in a core format.

Is RSC-032 an error?

RSC-032 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.