# Cloudflare makes Python Workers generally available after two-year preview

> Simon Willison reports Cloudflare's Python Workers left a two-year preview and are now stable, running Python on WebAssembly via Pyodide in the V8-based workerd runtime.

- **Topic**: Models
- **Published**: 2026-09-23T16:22:13.961Z
- **Canonical URL**: https://highsignal.sh/stories/cloudflare-makes-python-workers-generally-available-after-two-year-preview-2f5c873e

## Why It Matters

Python is now a fully supported language on Cloudflare's developer platform, but the WebAssembly VM has documented limits — Simon Willison notes multiprocessing and threading are non-functional.

## Key Findings & Analysis

### What happened

Cloudflare's Python Workers support is now generally available, leaving a two-year preview, according to Simon Willison. Willison writes that Cloudflare runs Python compiled to WebAssembly via Pyodide in its V8-based workerd runtime, and describes the release as a significant investment in the wider Python ecosystem. He notes the release announcement is credited to Gyeongjae Choi, Dominik Picheta, and Hood Chatham, with Gyeongjae and Hood both Pyodide core maintainers.

### Limits and local development

Willison reports documented limitations, most notably that multiprocessing and threading are non-functional in the WebAssembly VM. He also highlights the local development environment: the pywrangler tool (packaged as workers-py on PyPI) runs a full local simulation of Cloudflare's stack, including executing code with Pyodide in WebAssembly in V8 in a 123MB workerd binary, which for him ended up in node_modules/@cloudflare/workerd-darwin-arm64/bin/workerd.

## Original Evidence & Verbatim Citations

> "Cloudflare Python Workers are now generally available"

— *Grounded field: headline*

> "After a two year preview, Cloudflare's support for running Python code in their server-side Workers platform is now stable"

— *Grounded field: summary*

> "Cloudflare are running Python compiled to WebAssembly via Pyodide in their V8-based workerd runtime"

— *Grounded field: summary*

> "Python is now a first-class, fully supported language on the Cloudflare Developer Platform"

— *Grounded field: whyItMatters*

> "most notably both multiprocessing and threading are non-functional in the WebAssembly VM"

— *Grounded field: whyItMatters*

> "After a two year preview, Cloudflare's support for running Python code in their server-side Workers platform is now stable"

— *Grounded field: section:0*

> "Cloudflare are running Python compiled to WebAssembly via Pyodide in their V8-based workerd runtime"

— *Grounded field: section:0*

> "Python Workers represent a significant investment in the wider Python ecosystem by Cloudflare"

— *Grounded field: section:0*

> "The release announcement is credited to Gyeongjae Choi, Dominik Picheta, and Hood Chatham - Gyeongjae and Hood are both Pyodide core maintainers"

— *Grounded field: section:0*

> "This comes with some limitations, documented here - most notably both multiprocessing and threading are non-functional in the WebAssembly VM"

— *Grounded field: section:1*

> "their pywrangler development tool (confusingly packaged as workers-py on PyPI) runs a full local simulation of their stack, including executing code with Pyodide in WebAssembly in V8 in a 123MB workerd binary, which for me ended up in node_modules/@cloudflare/workerd-darwin-arm64/bin/workerd"

— *Grounded field: section:1*

## Primary Sources & Citations

- [Cloudflare Python Workers are now generally available](https://simonwillison.net/2026/Sep/21/cloudflare-python-worker/) — *Simon Willison* (Reporting)

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