Caveats

Typst's HTML export is young. These are the things that bite.

HTML export is experimental

Typst prints a warning on every compile saying so, and its authors reserve the right to change the behaviour. Bundle export carries the same warning. Treat Typst bundles as a preview rather than a production commitment.

Headings shift down a level, and that is fine

The exporter reserves h1 for the document title, so = in source becomes h2 in output, == becomes h3, and so on.

You cannot correct this in Typst: #set heading(offset: -1) fails to compile, because offsets must be zero or more.

You do not need to. The server normalises headings when it renders a page, so the shallowest heading on the page becomes h1 and the rest follow. Write = for the page title and == for sections, as you would for a PDF, and the result matches every other format.

Lists use a hyphen

- starts a list item. * is strong emphasis, so a line beginning with * is read as an unclosed delimiter and fails to compile. This is easy to get wrong coming from Markdown or AsciiDoc.

Pages cannot inherit setup

In a page-per-file layout each page is compiled on its own, so a helper or a #set rule defined in another file is not in scope. Import what the page needs from a partial. See Books and multiple files.

Not every element has an HTML form

Layout-oriented features have no meaning in HTML and are either dropped or reported as unsupported. Typst is a typesetting language first; its HTML output is a second target, not the primary one.

If a construct does not survive, that is a limitation of the exporter rather than of the bundle format.