{"slug": "opfs-pyodide-test-harness", "title": "OPFS + Pyodide test harness", "summary": "Simon Willison built a test harness combining OPFS and Pyodide to explore whether Datasette Lite can edit persistent SQLite files stored in the browser's Origin Private File System. The tool allows testing this capability across different browsers.", "body_md": "**Tool:** [OPFS + Pyodide test harness](https://tools.simonwillison.net/opfs-pyodide)\n\nI've been pondering if [Datasette Lite](https://lite.datasette.io/) - 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.\n\nThat's what [OFPS](https://developer.mozilla.org/en-US/docs/Web/API/File_System_API/Origin_private_file_system) (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.\n\nTags: [browsers](https://simonwillison.net/tags/browsers), [pyodide](https://simonwillison.net/tags/pyodide), [datasette-lite](https://simonwillison.net/tags/datasette-lite)", "url": "https://wpnews.pro/news/opfs-pyodide-test-harness", "canonical_source": "https://simonwillison.net/2026/Jun/23/opfs-pyodide/#atom-everything", "published_at": "2026-06-23 18:58:54+00:00", "updated_at": "2026-06-24 00:48:21.490817+00:00", "lang": "en", "topics": ["developer-tools", "ai-tools"], "entities": ["Datasette Lite", "Pyodide", "OPFS", "Simon Willison", "Claude Code"], "alternates": {"html": "https://wpnews.pro/news/opfs-pyodide-test-harness", "markdown": "https://wpnews.pro/news/opfs-pyodide-test-harness.md", "text": "https://wpnews.pro/news/opfs-pyodide-test-harness.txt", "jsonld": "https://wpnews.pro/news/opfs-pyodide-test-harness.jsonld"}}