RaTeX: KaTeX-compatible LaTeX rendering engine in pure Rust | Hacker News Reader

RaTeX: KaTeX-compatible LaTeX rendering engine in pure Rust

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188 pointsatilimcetin105 comments

I used LaTeX for approximately 10 years, for little things to relatively complex, including my bachelor’s and master’s theses. It never felt natural at reliable or consistent. Every customization required weird \makeatletter \makeatother hacks and was very brittle. Everything seemed more complicated than necessary and hard to grok, with weird interdependencies and interactions.

There are probably good reasons for all of that, but it is just both bad DX and bad UX. It feels like you need to be a hardcore LaTeX expert or consult with one, in order to accomplish the most mundane things. Especially in a reliable way, that won’t break upon making seemingly unrelated changes, or won’t break other things itself.

I used Typst for a few weeks. It already feels much more understandable, consistent, hackable, and customizable. I guess that is the difference between an ad hoc macro system and an actually thought through programming language.

The only drawback I can see is the ecosystem being smaller and less mature. That is, however, counteracted by being able to do things on your own, without immersing yourself deeply in LaTeX for years. Also, it will improve with time.

LaTeX is great, don’t get me wrong. But its heritage and historical baggage is really dragging it down.

It's kinda fascinating how dominant LaTeX is, how nice its output is, how respected Knuth is as a computer scientist, and at the same time how totally awful it feels to use it. Hard to figure out how it can be so good and so bad at once.

Posts/discussion I found interesting:

- http://www.goodmath.org/blog/2008/01/10/the-genius-of-donald...

- https://tex.stackexchange.com/q/24671

- https://news.ycombinator.com/item?id=15733381

In particular it's interesting how people seem to think TeX itself is actually quite nice to use but its popularity and LaTeX packages created a huge mess of a system.

Well -- TeX is "80s good". We've gotten better at designing ergonomic software since and it really doesn't meet the modern standard. But it's good enough for most people, and sufficiently hard to replace, that it has stuck around.

Added to that, academics specifically are more willing to suffer old crufty stuff than software engineers tend to be. After all their job is to absorb fields of material whether good or bad, and the technology tends to be lagging behind the bleeding edge in many subfields anyway so TeX doesn't even necessarily stand out.

> TeX is "80s good"

Bingo. Compared to troff and what preceded, TeX was amazing just in its usage. But its real value was in the quality of its typesetting. Knuth put a lot of effort into the beauty and historical correctness of the output, so much so that it was solving optimization problems to calculate line breaks. MS Word still can't break a line properly in 2026.

If TeX is “80s good”, Typst might be “90s” good, being generous.

Celebrating batch-mode typesetting in 2026 feels like some weird cyberpunk fixation.

Programmable like Emacs (but via Scheme), interfaced with major Computer Algebra Systems, tree-structured documents that are live-queryable and modifiable, and typesetting that rivals TeX without using TeX - TeXmacs provides all that, and much more (https://www.texmacs.org/tmweb/home/videos.en.html)

erg. You're not wrong but TexMacs looks like more 80s software that no one wants to use anymore because the user experience is awful.

There was a point in the 1990's where microsoft word wasn't truly WYSIWYG. IIRC it was like an infinite page and the line breaks and page breaks were "estimates"

Further many docs from that era are plagued with abandonware.

TeX did one thing well for an era when often the only interface to the machine was over a Xyplex terminal server connecting to a tty at 9600 baud.

You're linking to posts from 15 and from 18 years ago. And the post from 2011 is about how Donald Knuth wrote TeX (not LaTeX) in the early 1980s. While TeX and LaTeX have fundamental design flaws, it is much less awful to use them these days, with a rich selection of rather robust packages available, that vastly reduce the need to go into hard-core LaTeX programming yourself.

I won't lie: It takes getting used to and you need to learn a lot if you want to achieve fancy complex typesetting effects. But - it's not half as inconvenient as it once was.

part of the challenge is the inherent irreducible complexity of the domain. "Make text look good on page" leaves lots of details unspecified.

another part is many people built their own solution to their own corner of this domain, and not all of them had the deep appreciation for how the rest of the TeX system works.

I hear similar complaints about "Make web page look good", which is popular but also a huge mess of a system.

> "Make text look good on page" leaves lots of details unspecified.

Even just a sane layout renderer is incredibly hard. A decade ago I wrote a bespoke DNA sequence typesetter (in svg) and I had claude build an extension, for whatever reason it chose to build it from scratch instead of using the components I had built, and it did everything wrong.

Because Knuth wrote TeX, not LaTeX. All the parent comment's grievances are about LaTeX features, not TeX.

to be fair to knuth, he had nothing to do with latex. it's conceivable that one could start over from plain tex and build up a different high level system. (then again perhaps some of the brittleness of latex comes from unavoidable issues with the tex layer; lamport is a very respected computer scientist too!)

It’s my understanding that Knuth has little to nothing to do with latex and he himself uses tex for his books.

The dichotomy comes from conflating the TeX syntax with tex macro system, both use backslash.

The backslash based syntax allows for some really powerful typesetting which is far above anything that exists today. At the same time, the use of backslash-based langauge right to the bottom in terms of macros is what is causing the frustration.

Typst kind of solves that by having backslash based syntax implemented in Rust.

I’ve been using Typst for years now. Wrote my PhD thesis in it [1] as well as a book. Works great; can’t recommend it enough. I usually barely use plugins because it’s either already included or pretty easy to write a bit of code yourself

[1]: https://github.com/rikhuijzer/phd-thesis

Didn't see a pdf of your thesis, except on your web-site[1]. But the version there (at least as it renders on my machine), has numerous formatting issues. For one egregious example, look at the letter spacing in the title and legend of Figure 2.2 (page 27): "civilia ns", "Pe rs ona lity s core". I'm sure the content is great, but using it as an example of Typst prowess, seems ill-advised.

[1] https://huijzer.xyz/files/f72fa09561f20162.pdf

I don't see any issues with the title of Figure 2.2, but the legend and the x-axis label have weird letter spacing indeed. It seems like images like this are standalone (https://github.com/rikhuijzer/phd-thesis/blob/main/images/pe...) and probably aren't generated by Typst. So perhaps the weird spacing is not Typst's fault.

Looks like the SVG was converted from an EPS file, and the resulting SVG contains individual glyph positions (advances) for the characters in "Personality score", but it doesn't specify a valid font, probably because the font name was mangled in the original EPS file (which is pretty typical).

So whether the resulting file looks right depends on whether the rendering engine chooses the correct font. Looks like it's supposed to be Nimbus Sans or something metric compatible with that, but the serif font chosen by Typst looks obviously wrong.

I took a look at the repo and it's probably the fault of the the SVG of the graphs, not of typist itself. Now, you could have used typst libraries to generate the graphs but back then (2 years ago I think?) it was probably a struggle.

Yea, I don’t see a point of criticizing minutiae from a thesis that has already been accepted, but I agree, the graphs look out of place and generally not in the same style of the other text. Also, I guess I am just really used to latex’s font, it just automatically gives an academic style that I do t get from this. Again, pure personal bias.

If anyone else is looking to make graph with typst, this can be done with https://cetz-package.github.io/ -- which is inspired by Tikz from the LaTeX world -- or https://lilaq.org/ which seems more appropriate for this type of data plotting

> look at the letter spacing in the title and legend of Figure 2.2 (page 27): "civilia ns", "Pe rs ona lity s core"

The legend and title were generated by Gadfly.jl.

Someone willing to use AI to convert the thesis to Latex so we can compare?

Wow. I was not expecting that topic when I clicked on the link you provided.

When I went through such a selection process years ago, we took all sorts of tests before and even after the selection process. Towards the end, the head instructor told us they don't really have a good way to measure who will make it through. What he did tell us though is that top physical fitness test scores were not indicative that a candidate will make it to the end.

Is there a PDF version or instructions for building your thesis? I'd like to read it.

How about adding a PDF release ;-)

I like LaTeX for the most part (I have had to use some weird hacks but usually once they are done they are stuck in a macro and turned ignorable).

But I think the main things it has going for it are that it: produces nice output, and all the journals accept it. Does there exist a tool that renders Typist to LaTeX? That could play nicely with the existing ecosystem.

Pandoc can convert LaTeX to Typst and back but probably only for simple snippets without any obscure packages. It’s not lossless.

Huh. My special lady friend is in the process of finishing up her thesis using LaTeX after ditching LibreOffice. It was nightmare for some of the same reasons: bad UX, bad portability and crippling bugs. There was a ramping up period, and she had an out of date GitHub repo to help her, but she is incredibly happy that she switched. Collaboration could be smoother I guess.

Latex is used because writing math in latex is very good, and despite how everything else (like tables and figures) is so bad.

That's why people take the math subset of latex and use it in other contexts - exactly like this product.

I agree that tables are not great, but figures? Seems to work pretty well, better than word for sure.

I still find it easier to align tables with numbers in TeX on the decimal point than in anything else.

How is this even achieved with HTML or Word?

Eg. variable width numbers like

           4.53
          13.98765
           7
  -1,000,234.76

Not perfect in TeX either, but at least possible.

In Word you add a decimal tab stop to the ruler. Word's main problem is that people are unaware of its features; they don't spend time learning it like they do with TeX.

https://imgur.com/jipZ90B

Thanks, yeah, I haven't heard of it before even though it seems to have existed forever.

To your point, I guess that is an issue with WYSIWYG tools: if not discoverable, you assume it is not there.

The irony of your comment...

If you are not referring to the use of exaggerated examples to more clearly show the point, I wonder what do you refer to?

Not a latex post with someone talking about typst. Come back when the html output works. Not having good accessible output was more acceptable back when Tex was invented, it definitely isn’t now, and they made a new system and somehow got this worse then modern latex.

Typst does have have accessibility features.[1]

I don't worry too much about HTML output still being WIP. Even if TeX had a massive head start, Typst has a good development speed, and a little bit of slope makes up for a lot of y-intercept.

[1]: https://typst.app/docs/guides/accessibility/

This mirrors my experience.

It's worth noting that TeX was developed in the same time period that the details of lexical scope were being nailed down by Guy Steele in the Rabbit compiler for Scheme. It's not that TeX is an ad hoc system; it's more the case that people didn't actually know how to implement a better system at the time.

'People' in this case were Don Knuth (TeX) and Leslie Lamport (LaTeX). Both are Turing Award winners.

That's true. Do you know who else won a Turing Award? Tony Hoare.

What is Tony famous for? Well, lots of things, including his very important comparison sort algorithm Quicksort, but, in this context how about the Billion Dollar Mistake ? That's a pretty nasty booboo in many programming languages for which Tony blames himself because it was his idea.

Like your parent said, TeX shipped a long time ago and we learned a lot since then, it is not a surprise that we know how to do better today, in fact it would be a serious black mark for Computer Science if we couldn't.

Which means what, exactly.

The details of lexical scope where defined in Algol 60 (1960), nearly 2 decades before Rabbit (1978).

People did know how to implement things back then, and TeX is a great example of that. It is just our definitions have changed over the years of what we consider better.

Rabbit was closure conversion, which was efficient implementation of first-class functions with lexical scope. The abstract discusses the difference with ALGOL:

https://dspace.mit.edu/handle/1721.1/6913

Not necessarily my experience. I wrote (and I am writing) several academic documents with it. There are its quirks, of course, but with good classes such as memoir, I don't feel the need to do a lot more than basic customization in the preamble. Still is a good tool for me.

For me the memoir class made LaTeX worse. The titlesec package is more customizable, easier to use, and reduced the size of the preamble significantly.

That's if you need to customize headings. I usually can keep using the standard ones, so that's not my case, and I suspect this also applies to a lot of people.

Customizing chapter styles, page styles, and headings was my sole reason for using the memoir class. I'm probably in the minority, that's true.

I have been (and still am, I guess) a big LaTeX fan. I wrote a flora in LaTeX, with the idea that it would be a "living document" that I could update easily. That was a mistake. LaTeX really is very brittle. My flora no longer makes it through typesetting without erroring out, and trying to figure out what is going wrong takes so much time (not the first time I have had to deal with this). My idealism got ahead of practicality. Looking back, I should have used Word and InDesign; that combo would have prevented so many headaches and been more stable.

Agree. Love latex and LLMs made it a lot more accessible but DX wise it's still a huge hassle, esp when it feels that it's easier to just generate HTML and PDF it from there.. I mean the best workflow is probably to write markdown, take a site you like, pick a color scheme and have Claude do the transformation along with a script to make it repeatable

> The only drawback I can see is the ecosystem being smaller and less mature.

This seems like the _perfect_ use for an LLM: systematically porting over as much of the "ecosystem" to Typst as possible. Is anyone doing that?

Two hours ago a coworker told me that he let an llm port his latex template to typst. According to him, it was perfect.

as long as the arXiv doesn't accept Typst, it's never going to be a real alternative to LaTeX. and the arXiv maintainers seem either hostile or indifferent to Typst

https://www.youtube.com/watch?v=zNZlAbCOjd8

doesn't appear indifferent or hostile

TL;DW: there is interest in supporting Typst, but there are roadblocks:

* Higher priority work currently being done on ArXiV (moving from Perl to Python/cloud)

* No "standard" Typst distro

* Support team needs to be re-trained for a new language

* Persistency: TeX has 30+ years of history; will Typst be around in 30 years? Will current code compile? Will existing documents be supported?

haven't watched it but my only data point for that claim is this post: https://www.reddit.com/r/typst/comments/1dcu3p8/i_contacted_...

Yups, I love the idea of LaTeX, LaTeX itself not so much.

I hope Typst eventually gets some equivalent to tkz-euclide, as I've never seen anything even remotely comparable.

Meh. For cross-platform, low hassle, just use LyX + XeTeX + decent fonts. Once you learn how to do the commonly annoying things (alignment; indices; pages without footers; custom footers; etc. - AI is good), you can achieve all of them. You will positively loathe using conventional word processing after a short while. https://www.lyx.org/

Oh, wow, there's a new LyX release! It's been almost 30 years since I used it and it's still going.

I agree re. LaTeX. I've tried Typst for some complex projects, and it's just not quite there yet. ConTeXt on the other hand ... chef's kiss.

+1 for Typst being amazing.

I can actually like write my own functions when I need to. I don't think I have ever written a LaTeX macro without having to look up a lot of stuff.

Is Typst appropriate for web apps; e.g., the input forms here?

Nope. Typst's primary output is PDF, and it is a stand-alone binary. It's a replacement for most uses of LaTeX to produce documents. It is not a replacement for this project, which focuses only on rendering LaTeX math code and can be embedded in multiple different runtimes.

I know exactly what you mean, and that paired with a community that is absolutely sure that they know exactly how things need to be done and everyone that wants it in another way is dumb.

You want Typst: https://github.com/typst/typst

It's like the JSX of Latex: markup in a programming language, not a programming language pretends to be markup.

> I used Typst for a few weeks. It already feels much more understandable, consistent, hackable, and customizable. I guess that is the difference between an ad hoc macro system and an actually thought through programming language.

> The only drawback I can see is the ecosystem being smaller and less mature. That is, however, counteracted by being able to do things on your own, without immersing yourself deeply in LaTeX for years. Also, it will improve with time.

Pixel-diff CI against a golden suite is the right discipline for layout libraries, and it's noticeably rare in the JS ecosystem.

Most "matches KaTeX" claims I've seen in the wild rely on screenshot eyeballing, which collapses on edge cases like spacing primes, integral subscripts, and matrix delimiters that scale.

One thing I'd be curious about: how are font fallbacks handled when the same Rust core ships to platforms with different system font availability?

KaTeX bundles fonts and assumes they load cleanly; CoreGraphics and Skia bring their own glyph caches and metrics.

Does the display list carry metric snapshots from the host text shaper, or does the core compute layout from a bundled metric file independent of the backend?

In this case it doesn't eyeball same as it scores itself It self scores:

  157 \char"263a

as strong, while left is black circle smiley and right is full color emoji.

It's interesting to me that the page doesn't describe the size of the rust binary (relevant for mobile app use cases where you would need to add the Rust binary to your app) or performance.

The webpage also does read like it was at least heavily LLM assisted, which makes it a bit hard to trust it.

That all said, this is definitely something I'd be interested in using for Zulip if is indeed going to be a well maintained open source project.

(We currently have a node server component that the Zulip server runs only the render LaTeX).

> the size of the rust binary

The `render` binary weighed 4.0 MB on disk when I compiled it a few minutes ago. Not sure if that's what you were looking for, but just in case it is, there you go.

Here's the logs, if you want: https://gist.github.com/ethmarks/8df92a68c3076ea2f4a5aedba9f...

When developing KeenWrite[1], I opted to support only plain TeX. This is because I wanted math typesetting to work for either LaTeX or ConTeXt[2]. To render TeX in the preview panel, I forked NTS[3] into a highly optimized Java version. The lack of cross-platform event-based UI system is what kept me from writing the entire application in Rust (some ten years ago). Has the Rust ecosystem improved with respect to Markdown processing, event-based UIs, and now TeX support?

[1]: https://keenwrite.com/screenshots.html

[2]: https://wiki.contextgarden.net

[3]: https://ctan.org/tex-archive/systems/nts

I suppose somebody has to ask (and most likely complain) about this: what does RaTeX do for accessibility? I gather that it produces images. I checked the demo, and there's not even an alternative text or an ARIA label, so this seems completely invisible to anybody relying on a screen reader. This is quite a step backwards compared to modern LaTeX, which can now tag equations with MathML within the PDF, or using MathJax, or any other serious tool targeting HTML, like pandoc or LaTeXML.

Is accessibility anywhere on the roadmap for RaTeX?

AFAIK, KaTex has accessibility via MathML included, but it doesn't provide an export as image - it rather renders as html. So why would you want the utility that you use to render an additional image to take care of something that KaTeX already does?

True, my knee jerk reaction came from seeing this run in the browser... but that does not change the question. RaTeX advertises itself as a renderer for native apps, but how are those apps supposed to implement accessible controls? Does RaTeX offer anything towards that?

Honestly, I have no idea how native apps for desktop or mobile handle accessibility. There is katex-rs[0] that outputs html and mathML. I'd assume the two could work together and the mathML would be fed to whatever the screen reader receives instead of the image?

On a related note: is mathML more accessible than an AI generated text of how a human would read the mathematical or chemical formula?

[0] https://crates.io/crates/katex-rs

> On a related note: is mathML more accessible than an AI generated text of how a human would read the mathematical or chemical formula?

Yes, screen readers would typically allow you to navigate the formulas in ways that are more sophisticated than text (not to mention the issues with translating to Braille, which I don't claim to understand, at all). In fact alternative text is a poor substitute for structured information about the formula, which is what you get with MathML.

Plus, the MathML + screen reader combo is deterministic and debuggable, as opposed to OCR'ing an image.

> There is katex-rs[0] that outputs html and mathML. I'd assume the two could work together and the mathML would be fed to whatever the screen reader receives instead of the image?

Maybe! You are parsing the input twice, but it could be a pragmatic solution. I don't know myself how native apps are supposed to expose MathML to screen readers (or if it is even possible without an embedded browser!).

I'm working on a Neovim plugin to render LaTeX in Markdown, and I'm struggling with this. Why is it so hard to simply render an image from KaTeX?

What are you struggling with? If you want an image output, there a reason you want to use KaTeX for this, and can't just use actual LaTeX?

KaTeX depends on the browser engine to do most of the layout, so generating an image would require a tool which converts the HTML nodes back into an image. There are some tools that can do that (like html2canvas), but using LaTeX to generate a PDF and then converting that to an image is probably going to be easier.

I am so confused. There's already a native version of LaTeX... it's... it's LaTeX. Why would a Rust implementation need to match KaTeX instead of properly implementing a real (and modern, so unicode-out-of-the-box) TeX engine, that LaTeX (which is a set of convenience macros) then trivially runs on top of?

Btw, the unicode-out-of-the-box version of LaTeX is called LuaLaTeX and ships with TeX Live.

I think you'll find XeTeX (with XeLaTeX because no sane person uses plain TeX except for package authors of course ;) predates LuaTeX by almost a decade.

(Something I ran into in 2008 when I was writing a multilingual book and heard about LuaTeX, only to find out it was still extremely incomplete and was roadmapped to not be done until 2012. And I couldn't wait 4 years)

Despite the "Gold-suite" comparison, when looking at the KaTeX and RaTeX output [1], the KaTeX output is consistently better. RaTeX has either a lot of aliasing going on or appears blurry.

But the native and library nature of RaTeX is very interesting, especially with the provided C ABI.

[1] https://ratex.lites.dev/demo/support-table

Are you viewing on a HiDPI monitor? I imagine this is mostly because RaTeX renders to an image whereas KaTeX is rendering HTML, so can scale to arbitrary dpi. I imagine the RaTeX people could have rendered to a higher resolution and it would look better.

I'm not sure how much overlap there is between this project and Tectonic [1], but that's what I use personally for local PDF generation, and it's also using a good bit of Rust.

Just thought I'd mention since it's related and I really like the project.

[1] https://github.com/tectonic-typesetting/tectonic

The landing page (clearly to a large part written by LLM) does not mention that both KaTeX and mathjax can render to SVG in node. This wasm approach might still be lighter, but the advantage is not as clear as the page makes it seem. (It also contains LLM dishonesties like that the bundle size is 0 KB.)

Where this clearly wins is native rendering use cases where there is no browser or JS engine involved at all.

A sphinxdoc ratex Makefile task for building from .rst and .md doctrees to PDF?

There are probably enough tests for a Rust rewrite of docutils and sphinx with Python extension compatibility; docutils.rs and sphinxdoc.rs?

> It also contains LLM dishonesties like that the bundle size is KB

That one jumped out to me too. The phrasing is so wiggly but technically correct it feels intentional. When I saw it I didn't blame it on the LLM, which is worse.

Otherwise it's a super cool looking project

If RaTeX gets to brag about having a 0 KB JS bundle, the other libraries should be able to say they have 0 KB WASM bundles!

I wish it was standard for projects to say the extent to which they were vibe coded, in the same way that they give a license.

Interesting. Reminds me of Typst (both implemented in Rust and replacing TeX to some degree) and Microtex.

I greatly prefer Typst's clean architecture than TeX's macro-centric hell pounded into passable utility.

I have been using Typst for creating notes and it is an awesome tool. I use it to create notes on welding for my students. It makes my life so much easier compared to badsoft and its not-word-ing (you understand me).

I've discovered typst in the last year and used to build a resume and cover letter template that feeds from a YAML file.

After a bit of tinkering and understanding the idiosyncracies of Typst, the joy of having reliable, consistent, beautiful, data-driven resumes and cover letters is not measurable. It basically lifted any barrier to applications, while whatever I had before I had always considered a burden.

On top of that, I can add hiring process data directly to the yaml file to run further analysis.

Can LaTeX do this? Most probably, but the learning curve is the difference.

We recently switched from Node.js + Mathjax for rendering latex to Goja (https://github.com/dop251/goja) + Mathjax, and surprisingly it worked really well. We did this because the app is already 99% golang, and this allows us to eliminate the remaining non-go pieces, greatly simplifying the SBOM. And yes, we tried go-latex, but it's not nearly as feature complete as Mathjax. Not to mention using goja + Mathjax adds 10MB to binary size while Node.js adds 200MB+

I switched to Typst a year ago and never looked back

I don't know why but this chain amuses me: RaTeX -> KaTeX -> LaTeX.

I guess it shows how everyone loves but hates LaTeX and is always trying to bolt on that one last thing that will make it good.

Aren't these 3 different implementations with totally different use cases? Katex is latex-like implementation for web. Ratex is really 'rewrite katex in rust'. I don't understand what is getting "bolted on" to what here.

Interesting! Would love to see how RaTeX evolves.

> JS bundle (typical) 0 kB JS (core is WASM)

I guess you should mention how much is WASM, right?

Anybody embed it in a markdown renderer yet?

> JS bundle (typical) 0 kB JS (core is WASM)

Hello?

Trolling aside, I found this kind of Rust-powered typeset modernization promising. I used Typst and liked it. This one would have its own niche too.

I'm sorry but the only thing that truly understands TeX, is, and will forever be, TeX.

And 64kb should be enough for anyone.

A native Rust alternative to KaTeX is a welcome addition. This should make math rendering much easier to integrate into Rust based static site generators.

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