Should Notes Be Indexed?

In a book, notes — footnotes or endnotes — can serve a couple of purposes: they either provide supplemental information about something discussed in the text, usually as an aside so it doesn’t quite fit in the main body of the text, but important enough that the author(s) wanted to inform the reader about it, or they are bibliographical and only contain source citations.

Bibliographical notes do not typically get indexed in a standard back-of-the-book index.*

Sometimes, notes simply provide a reference to guide readers to other books or resources on a topic (e.g., “For more information on this, so-and-so’s book…”). These are the least likely to be considered for inclusion in the index, since the information they contain is not itself substantial.

Notes that truly provide supplemental information are good candidates for inclusion in the index because they contain actual discussion about a topic that may be useful to the reader.

While it could be argued (against the indexing of any notes) that people who are interested will find that information by reading the text and following the reference to the note, their inclusion in the index will present readers with a one-stop shop to find all relevant information about a topic.

In short, nothing but the reader’s time might be lost by excluding notes from an index.

That being said, since saving the time of the reader is a shared tenet among indexers and librarians, it is deeply embedded in my DNA to want to index notes that provide substantial information.

For more on indexable content, see this post: Indexable Pages: What to Include

*An argument could (and has) be made, by none other than Nancy Mulvany, for indexing bibliographic references.
Time and space restrictions are usually the most pressing arguments against the practice, and the question of exactly how much it would benefit readers should definitely be weighed against the time and effort that would go into indexing those bibliographic notes.
— CMS (17th Edition), in section 16.110, simply says that bibliographic notes “need not be indexed.”

— I, personally, like the idea of indexing bibliographic notes but I also understand that it is often, totally impractical.