Rheo

Why do we need Rheo?

Rheo (ree-oh) is an open source typesetting and static site engine for Typst. It is a typesetting engine because it produces typeset digital documents such as PDF and EPUB, and a static site engine because it produces websites that don’t require communication with a custom backend server, but rather are self-sufficient sets of files that can be natively opened a browser (static sites). Most static site engines these days employ Markdown, a markup format that is approachable and pretty generic, allowing folks who are not familiar with or otherwise don’t want to deal directly with the required file formats of the web— HTML, CSS, and Javascript— to write blog posts and other content which can then be pumped into a static site.

As useful as it is, Markdown has its ambiguities. For one, there isn’t a standardized syntax for citations or footnotes. Though extensions exist that can produce these, they are not supported in the core Markdown syntax, meaning that it’s not really Markdown and can’t be relied upon to work in all contexts that support Markdown. Markdown is great when using hypertext (hyperlinks, images, etc). It’s not so great when it comes to things like tables, figures, and math.

Typst is a markup language that integrates with plain text, like Markdown, making it easy to adopt and joyful to write. Unlike Markdown, however, it is also a Turing-complete programming language with a modern type system, meaning that it is possible (though not necessary) to express sophisticated conditional logic controlling where and how text is rendered. Typst has a concrete and concise syntax for footnotes and citations, and can express visual constructs such as tables, figures, colors, and mathematical formulas. It was developed as a modern alternative to LaTeX, Leslie Lamport’s legendary 1980s addition to Donald Knuth’s original ‘78 Tex typesetting system. For the past 40 years, LaTeX has been the most expressive way to produce PDF documents, rendering it the de facto standard for academic and scientific publication. In the past few years, Typst has become the most promising and powerful alternative to LaTeX due to its maintainers’ effort to build out a reliable PDF compilation toolchain.

In 2025, Typst added experimental support for HTML compilation. Though there are still many features in Typst that will only produce meaningful output in the PDF toolchain, the HTML toolchain now supports all of the essential features for academic documents in the humanities: text decoration, headings, hyperlinks, footnotes, and citations.1 This makes it an extremely good replacement for Markdown as a markup language in a static site engine, and so: enter Rheo.

Rheo is a CLI (command line interface) that produces PDF, HTML, and EPUB simultaneously from a folder of Typst documents. It is a static site engine because it can produce a fully valid website: all it needs is a folder containing valid Typst. Rheo also provides mechanisms to combine multiple Typst files into a unified EPUB or PDF, making it a tool that improves the experience of writing books, dissertations, or any other long-form text in Typst. On the other side of the same coin, Rheo allows you to produce an offline version of a website such as a blog written in Typst through its PDF/EPUB toolchain.

Rheo allows you to compile multiple Typst files that link to each other into a single output, adding what is needed (relative linking) in order to make Typst an ideal markup language for writing static sites. Typst is the most elegant and flexible way to typeset PDF documents today; Rheo extends Typst’s capabilities, allowing you to additionally typeset EPUBs and generate static sites from the same source.2 Naturally, this blog post was written in Typst, and this site was made with Rheo. If you’re already convinced, feel free to jump ahead to Getting Started to download Rheo on your system and start writing.

The philosophy of Rheo

Rheo is a prefix or combining form in English that originates from the Greek word rheos (ῥέος), meaning flow, stream, or current. Rheo flows Typst documents into a number of concurrent output formats in PDF, HTML, and EPUB. But other meanings lurk beneath the surface of this basic idea. Sarah Pourciau has argued that the oceanic is a deep-rooted metaphor in computing, as all computation at some level seeks solid space in a sea of digital noise (Pourciau 2022). From Alan Turing’s partial solution to David Hilbert’s Entscheidungsproblem in the universal machine, to Claude Shannon’s information theory, to Leslie Lamport’s ordering of events in a distributed system, the key issue at hand is how to carve out clarity from uncertainty and confusion. Writing has played a magisterial role in calming the storm of imprecise thought. Long before computation arrived on the scene, the written word has served as the steward of reason, in the Western world and beyond, from Mesopotamian cunieform to Twitter. Nota bene (‘Take note’): that writing can also herald chaos and confusion doesn’t invalidate its capacity for spreading sensibility.

Rheo is a tool that facilitates the production and publication of documents following from the original vision of the Internet as a mechanism for lively and reasonably unfettered academic exchange, rather than the densely commercial space of platform capitalism that it has become. It should not be so difficult, given the extraordinary capacities of software and hardware today, to make a piece of writing publically available in a plain and pleasant format. That there exist digital humanities initiatives measured in months and years to bring books to the web as basic websites is a clear sign that something has gone awry.3

Rheo aims to enable the publication of more books, blog posts, and papers without the necessary capitalist ceremony of creating an account on Substack, Medium, or Squarespace. A website without any interactive elements such as forms, online marketplaces, or comments should be simple to set up, as it isn’t rocket science in 2025 thanks to all the hard work that folks have put into Internet protocols and web standards. It should be simple to create a PDF or EPUB for sharing with colleagues or collaborators—as simple as it is to send an email.

This is the vision of the world to which we at the free computing lab aspire, and in search of which we have built Rheo. Rheo is the first installment in a larger set of writing tools we aim to build, which will include processes for collaboratively drafting documents, constructing and working with digital libraries, and more.

Bibliography

Footnotes

← Introduction Getting started →
← Previous Next →
  1. 1 I qualify this with ‘in the humanities’ as scientific papers often require tables, figures, and mathematical markup. These features are on Typst’s roadmap for html, but are not yet available at time of writing (January 2026).
  2. 2EPUB is on Typst’s roadmap, but is not yet natively supported.
  3. 3 There are many exciting and experimental ways of presenting text and other conent in the digital humanities. But we think that it should be easier that it currently is to publish and distribute books digitally, simply and straightforwardly.