EpubCCWhat is remote resources in EPUB?
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A remote resource is a file an EPUB loads from the web instead of carrying it inside the ZIP. EPUB 3.3 allows it only for audio, video, fonts and resources fetched by scripts; everything else, including images and stylesheets, must be inside the container.
Why it matters when you convert a PDF to EPUB
An e-book is read offline, on planes and on e-ink devices without a browser, so anything loaded from the web may simply be missing. PDFs that link to images or fonts online, or HTML copied from a website, are the usual way remote references sneak into an EPUB.
A content document that does use an allowed remote resource must say so with the remote-resources property on its manifest item. EPUBCheck reports a forbidden remote reference as RSC-006, a missing property as OPF-014 and a declared property with nothing remote as OPF-018.
How EpubCC handles it: everything the engine writes is inside the container, so its EPUBs never reference remote resources. Links in the text to websites are ordinary hyperlinks, which are allowed.
Related terms
EPUBCheck messages about this
RSC-006Remote resource reference is not allowed in this context; resource "…" must be located in the EPUB container.OPF-014The property "…" should be declared in the OPF file.OPF-018The "remote-resources" property was declared in the Package Document, but no reference to remote resources has been found.
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