Simon Willison’s Weblog

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23rd June 2026

Tool OPFS + Pyodide test harness — Test and manage the Origin Private File System (OPFS) across desktop and mobile browsers with an interactive interface powered by Pyodide. Create, read, and delete files in OPFS, run SQL queries against SQLite databases stored in the file system, and verify persistence across page reloads through a comprehensive activity log and capability detection panel.

I've been pondering if Datasette Lite - the Python Datasette application run entirely in the browser using Pyodide and WebAssembly - might be able to edit persistent SQLite files stored on the user's computer.

That's what OFPS (Origin Private File System) is for, so I had Claude Code for web build me this playground UI to try it out in different browsers.

This is a beat by Simon Willison, posted on 23rd June 2026.

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