quarto-index extension: one back-of-book index for PDF, HTML, EPUB and Typst

[jmgirard]

Quarto has no built-in subject index. For PDF you can load makeidx and write \index{} by hand. Those marks do nothing in HTML, and you have to add \printindex yourself. This has come up here several times: #3849, #5579, #8251, #10213 and #12249.

quarto-index is a filter extension for this. You mark a term once, in Markdown, and each output format gets its own index:

• PDF (LaTeX): \index{} entries through imakeidx, with page numbers, listed in the table of contents.
• HTML: an Index section with entries that link back to each mark.
• EPUB: a linked index.
• Typst: a two-column index with page numbers, and no Typst package to install.

In other formats, such as Word and reveal.js, the marked text passes through unchanged.

Install it in your project:

quarto add jmgirard/quarto-index

Then turn on the filter:

filters:
  - index

Marks are spans, so the visible text stays as you wrote it:

[Bayes' theorem]{.index}                              <!-- indexed under its own text -->
[the posterior]{.index entry="Bayesian inference!posterior"}   <!-- sub-entry -->
[]{.index entry="Markov chain Monte Carlo"}           <!-- entry with no visible text -->
[MCMC]{.index see="Markov chain Monte Carlo"}         <!-- see reference -->
[Gibbs sampling]{.index mention="principal"}          <!-- emphasized locator -->
[Cantor]{.index index="people"}                       <!-- goes in a second index -->

It also handles see-also references, page ranges, sort keys, and marks in figure captions and image alt text. One document can hold several named indexes, for example a subject index and an index of names. The index heading and the see words follow your lang: for Spanish, French, German and Italian. (Let me know if you need another language added.)

A Quarto book gets one index for the whole book. Put this marker where the index belongs:

::: {.qi-index-here}
:::

In an HTML book the marker chapter must come last. Quarto renders each HTML chapter on its own, and the index collects the chapters before it. Run a full quarto render before you publish so that the index is current. PDF and EPUB books do not have this limit.

It needs Quarto 1.5 or later. Continuous integration renders the example fixtures on Quarto 1.5.52 and on a current release, and compares the indexes they produce.

Docs: https://jmgirard.github.io/quarto-index/
Source: https://github.com/jmgirard/quarto-index

Bug reports and feature requests are welcome as issues on the repo.