It works surprisingly well in terms of writing python for native execution, and then trying to share on the web and having it Just Work TM. Unfortunately, when I want python it's because I want numpy, scipy and friends, and once you bring them on board pyodide load times are long. As an example comparison: a face turning octahedron puzzle in python + pyodide, loads in 10 seconds https://cubes.hgreer.com/fto.html . Meanwhile, a megaminx puzzle in javascript (statically generated by python) loads in 200 ms https://cubes.hgreer.com/ssg/output.html
Pyodide is one of the hidden gems of the Python ecosystem. It's SO good at what it does, and it's nearly 8 years old now so it's pretty mature.
I love using Pyodide to build web UIs for trying out new Python libraries. Here's one I built a few weeks ago to exercise my pure-Python SQLite AST parser, for example: https://tools.simonwillison.net/sqlite-ast
It's also pretty easy[1] to get C or Rust libraries that have Python bindings compiled to a WebAssembly wheel that Pyodide can then load.
Serious question: why would you use Python on the web? Unless you have some legacy code that you want to reuse. Performance is somehow worse than CPython, C-extensions are missing, dev experience is atrocious.
There's also xeus-cpp which is cpp based on wasm. Xeus-cpp and pyodide are the backends for Jupyterlite [1] kernels in browser.
It's actually a very good way to teach coding in python/c++(11, 17 or even 23), explore language features or your own library within browser and allow students to execute code by hosting just some static html pages and some assets without any backend.
That is very cool. Has anyone made a nice beginner's learning environment out of it? Seems like it would solve some of the extra friction that makes it hard to get started.
Pyodide powers xlwings Lite, a free Excel add-in that you can install from Excel’s add-in store with a single click. It outperforms Microsoft’s official Python in Excel solution in every coceivable way: price, privacy, speed, can install packages, can access the internet, can access local files, doesn’t have a usage quota, can automate Excel and create native UDFs. See https://lite.xlwings.org
This is not funny. Sure, i have a technology that is a little bit slow, but i can run it nearly everywhere. Almost every day, there come a new desktop, OS, etc... but very soon a runtime for webassembly. It is good for that, what i call little data quick fixes.
Love all the tools mentioned in the comments, Pyodide is a fun tool. I built https://pyground.vercel.app with it a few years ago, as a quick way to run Python on a CSV/JSON file locally in the browser. For a while Python/Matplotlib was what I was most comfortable writing quick and simple analysis scripts with, and this was my go to for one-off data analysis work. You can drag-drop a file in, then some 'clever' code makes it available as `data` in the Python script so you don't have to write any parsing code yourself.
Now I'd probably just get Claude Code to write something locally, but there might be some value in a version of pyground that can use an LLM to write the Python code for you (and give it the data shape) but keeps the local execution setup the same.
A reactive notebook for Python that runs in browser, powered by Pyodide. I have been using it extensively for teaching Python to non-STEM students that do not need the added friction of navigating the CLI or filesystem hierarchy.
related self plug: I built https://codeglf.com on Pyodide, a weekly Python code golf site where every submission runs locally in the browser.
WebAssembly's isolation means you get sandboxing for free without any server infrastructure. Of course users could cheat and submit code that doesn't actually pass the tests, but so far everybody has been friendly and I haven't needed to validate results server-side. Hopefully sharing the link here doesn't make that worse!
It’s impressive how mature Pyodide has become — running Python scientific tools in the browser opens up a lot of possibilities.
I’ve been working on a small (~800-line) Python system that uses sparse regression to discover physical laws from raw data. It was able to estimate the Sun’s rotation (~25.1 days vs 27 days actual) and found a temperature ~ velocity^3.40 relationship in solar wind data.
Having this kind of lightweight stack in the browser could make exploratory science much more accessible.
28 comments
[ 2.3 ms ] story [ 53.6 ms ] threadhttps://nvd.nist.gov/vuln/detail/CVE-2025-68668
https://nvd.nist.gov/vuln/detail/CVE-2025-51464
https://nvd.nist.gov/vuln/detail/CVE-2026-25905
I love using Pyodide to build web UIs for trying out new Python libraries. Here's one I built a few weeks ago to exercise my pure-Python SQLite AST parser, for example: https://tools.simonwillison.net/sqlite-ast
It's also pretty easy[1] to get C or Rust libraries that have Python bindings compiled to a WebAssembly wheel that Pyodide can then load.
Here's a bit of a nutty example - the new Monty Python-like sandbox library (written in Rust) compiled to WASM and then loaded in Pyodide in the browser: https://simonw.github.io/research/monty-wasm-pyodide/pyodide...
[1] OK, Claude Code knows how to do it.
https://jupyter.org/try-jupyter/lab/
Stuff like numpy seems to just work
It's actually a very good way to teach coding in python/c++(11, 17 or even 23), explore language features or your own library within browser and allow students to execute code by hosting just some static html pages and some assets without any backend.
1. https://jupyter.org/try-jupyter/lab/
Now I'd probably just get Claude Code to write something locally, but there might be some value in a version of pyground that can use an LLM to write the Python code for you (and give it the data shape) but keeps the local execution setup the same.
A reactive notebook for Python that runs in browser, powered by Pyodide. I have been using it extensively for teaching Python to non-STEM students that do not need the added friction of navigating the CLI or filesystem hierarchy.
not actively developed anymore
https://isaacgerg.github.io/remus-rlf-reader/webapp/
WebAssembly's isolation means you get sandboxing for free without any server infrastructure. Of course users could cheat and submit code that doesn't actually pass the tests, but so far everybody has been friendly and I haven't needed to validate results server-side. Hopefully sharing the link here doesn't make that worse!
I’ve been working on a small (~800-line) Python system that uses sparse regression to discover physical laws from raw data. It was able to estimate the Sun’s rotation (~25.1 days vs 27 days actual) and found a temperature ~ velocity^3.40 relationship in solar wind data.
Having this kind of lightweight stack in the browser could make exploratory science much more accessible.