title_body: What are epub JSON links? I've spotted that there are some links within the epub using a format in line with JSON
  
  &lt;a href="{&amp;quot;unit&amp;quot;: &amp;quot;U01&amp;quot;, &amp;quot;page&amp;quot;: 24, &amp;quot;exercise&amp;quot;: [&amp;quot;AB1&amp;quot;]}"&gt;
  
  
  the href look like this
  
  {"unit": "U01", "page": 24, "exercise": ["AB1"]}
  
  
  What are those links? are they described in the epub-3 specification? and how does the reader handle that kind of JSON href references?
upvoted_answer: The reader should just ignore it.
  
  According to epub standard which says content should be valid XHTML or HTML5 and then  following the links through to the RFC 3987 for an URI section 2.2 a href begins with a scheme (e.g. http) and then a :
  
  I would guess that there is a reader that preprocesses a file and this converts the JSON to a link.