I will give a lecture about Haskell next week and might use this website for demonstration.

Compilers are complicated. WASM has been a priority for the Haskell community for a while. Demonstrating GHC's ability to compile itself to WASM is thus a show that it is robust enough to compile a very complicated program into this backen.d

For one, it demonstrates how far the ghc wasm backend has come, in that such a large system as ghc itself can now run in wasm

Have you ever used Godbolt? The Rust playground? The Typescript's playground? The Go playground?

It lets you have that without the pain of hosting compilers server side.

From "WebR – R in the Browser" (2025 https://news.ycombinator.com/item?id=44999706 :

> jupyterlite-xeus builds jupyterlite, Jupyter xeus kernels, and the specified dependencies to WASM with packages from conda-forge or emscripten-forge.

jupyterlite/xeus https://github.com/jupyterlite/xeus

There may be an easy way to wrap GHC with jupyterlite/xeus, with Haskell's lazy evaluation; xeus-haskell or xeus-ghc?

yeah why would anyone want to run code on a website

It would be more plausibly practical if GHC could now target wasm, but this announcement is actually about being able to run the compiler itself in the browser.

It can target wasm, the point of the post is that it’s now mature enough to be able to build itself for wasm and run in a browser.

This is a show case of the wasm backend

GHC is built with GHC lol

Loading 50mb of WASM is a big tradeoff just to run code on a website.

Loading time is pretty rough, but it seems responsive enough after the initial load. Probably as fast or faster than downloading and installing GHC locally.

For comparison: the homepage of cnn.com right now is 33.37MB on my machine. 16.82MB of which is JavaScript.

I would assume that in the near future one can preload, cache, update selected WASM packages. I also imagine that sooner than that we can preload open models in the browser to run the natively instead of only invoking third parties (e.g. window.ai in the DOM)

I think the immediate and obvious case would be educational materials. Other than that, technical achievements need not always be practical to be cool :)

That’s one of the primary reasons we built the tooling for Q# to run in the browser (by writing in Rust and compiling to wasm). The “try with copilot” experience [1] and the “katas” for learning [2] all have a full language service and runtime in the browser.

https://quantum.microsoft.com/en-us/tools/quantum-coding

https://quantum.microsoft.com/en-us/tools/quantum-katas

Agreed. Too many people said Haskell is only for academia, yet we’re seeing more quality software being released in Haskell over the past few years.

We are? Please share.

I don't have the same impression, but https://github.com/PostgREST/postgrest and https://github.com/koalaman/shellcheck are some popular ones that may be useful to hn'ers.

And https://github.com/mchav/dataframe?tab=readme-ov-file#datafr... is a library/framework that has had quite some velocity lately

Pandoc is the first thing that comes to mind, but I also believe I have seen an uptick in software that I use being written in Haskell lately, though I can't remember what else off the top of my head.

In addition to the other responses, it's also worth noting that wasm itself is useful outside of the web itself; e.g. in containerized applications.

Teaching