# What is a noteref?

Source: https://epubcc.com/glossary/noteref/ (updated 2026-11-04)

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.