Willison: OPFS + Pyodide test harness for persistent SQLite in the browser

Key idea

A small exploratory tool probing the limits of the OPFS API for offline-first database apps – Datasette Lite runs in the browser via Pyodide and WebAssembly, and this harness verifies whether it can actually edit SQLite files stored locally on the user's device.

Context

Follow-on to Willison's earlier Datasette Apps work (June 18) and part of his broader push toward browser-native data tooling with no server backend.

Why it matters

OPFS is becoming a key API for local-first web apps; if Datasette can reliably exploit it, that opens the door to full-fledged database editors running entirely in the browser.

Details / arguments

• Harness built with help from Claude Code for web
• Tests cross-browser behaviour (Chrome, Firefox, Safari) for OPFS support
• Goal is persistent SQLite editing with no server