Preswald

Preswald is an open-source static-site generator for Python data apps that run in the browser with no server.

Preswald packages compute, data access and UI into a self-contained data app that runs locally in the browser. A WASM runtime with Pyodide and DuckDB executes Python and SQL without a backend, including offline. Apps are written in Python with built-in tables, charts and forms, and a reactive DAG reruns only what changed. One command exports a fully packaged HTML file that can be sent to someone who should not install anything. The authors position it for dashboards, reports, prototypes and agent-readable tools, especially when the data should stay on the reader's machine.

Preswald at a glance

Best for: Software engineer, Finance
Runs on: open source, Web
Pricing: Free and open source
Released: December 2024
Category: AI research tool
Website: preswald.com

Key features

Python data apps compiled to a single HTML file
In-browser Pyodide and DuckDB, including offline
Prebuilt tables, charts and forms
Reactive DAG so only changed steps rerun
No server and no local Python on the reader's machine
Inspectable structure meant for AI agents

Use it for

Send a stakeholder a dashboard that opens in a browser
Keep a sensitive dataset on the local machine
Prototype a report without standing up a web stack

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