EpubCCWhat is a noteref?
Updated:
A noteref is the link from a reference mark in the text (a superscript number or symbol) to its note, marked in EPUB 3 with epub:type="noteref". Reading apps that support it open the note in a pop-up.
Why it matters when you convert a PDF to EPUB
In a PDF the reference is just a small raised number, so a converter has to recognise it by size and position, keep it out of the word it touches, and turn it into a noteref link to the right note.
How EpubCC handles it: words break on a size ratio below 0.75, so a raised number does not stick to the word before it, and a second pass attaches loose superscripts to their line. When a superscript's label matches a footnote marker on the same page it becomes an epub:type="noteref" link, pointing to another chapter file when the note ended up there.
Related terms
EPUBCheck messages about this
RSC-012Fragment identifier is not defined.
See how EpubCC links footnotes
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