Turn Python scripts into shareable, interactive data apps.
Preswald is a static-site generator for building interactive data apps in Python. It packages compute, data access, and UI into self-contained data apps that run locally in the browser. Built on a WASM runtime with Pyodide and DuckDB, Preswald enables portable, file-based apps that are fast, reactive, and shareable.You can think of Preswald as a lightweight alternative to heavier web app platforms. It provides built-in UI components and reactive state tracking, so you can use it to build dashboards, reports, prototypes, workflows, and notebooks that are reactive, portable, and secure by default.Preswald now includes a fully automatic reactive runtime. This means you can write ordinary Python code, and Preswald will detect dependencies, track state, and trigger only the minimal set of updates needed when your data changes. No need to explicitly define which parts of your script are reactive, it’s inferred automatically.
Code-based development – Write apps in Python, not in notebooks or JS frameworks
File-first approach – One command creates a fully-packaged .html app
Built for computation – Use Pyodide + DuckDB directly in-browser
Composable UI – Use prebuilt components like tables, charts, forms
Reactive engine – Automatically tracks dependencies in your code and re-executes only what’s necessary, enabling fast, precise updates
Local execution – No server. Runs offline, even with large data
AI-ready – Apps are fully inspectable and modifiable by agents
High-performance GPU charts – Render real-time, interactive charts using fastplotlib, with offscreen GPU acceleration and WebSocket-based streaming to the browser