On 23rd June 2026, Simon Willison released a browser-based test harness designed to allow Datasette Lite to edit persistent SQLite files stored locally on a user’s computer. This capability relies on the Origin Private File System, which enables web applications to access files outside the sandboxed sandbox. Willison commissioned Claude Code to construct the user interface for this experiment, allowing the tool to function across different browsers. The project sits within a broader series of articles recently published on his blog, covering topics such as porting image inpainting models to the browser and updates to sqlite-utils.
The development demonstrates that Python applications running via Pyodide and WebAssembly can now interact directly with local storage without requiring a backend server. This removes the traditional barrier where browser-based tools could only read data or required users to upload files for processing. By granting write access to the local file system, the approach enables developers to build fully client-side data applications that maintain state permanently on the device.
* The Origin Private File System provides the necessary permissions for local file access.
* Pyodide executes Python code entirely within the browser environment using WebAssembly.
* Datasette Lite serves as the application layer managing the persistent SQLite database.
