It looks like Firefox is going to take a different route than other (Webkit-based) browsers, by adopting the “Indexed Database API”, rather than the “Web SQL API” for storage of local data in the browser, that are used by e.g. persistence.js. The Indexed Database API is a type of NoSQL database. You can store JSON-formatted documents in it and retrieve them. It does not support SQL. In a way this makes sense, as the proposed Web SQL standard was essentially dictating that SQLite should be provided by the browsers, which is not a great way of creating a standard — and would Internet Explorer ever include SQLite in its browser?