Fiddles are data and generally are transacted into a Datomic database. Which database is configured by URI, which you can see in the demo by clicking on "env" i

Fiddles are data and generally are transacted into a Datomic database. Which database is configured by URI, which you can see in the demo by clicking on "env" in the toolbar top right. If you self-host, you can instead opt to store your fiddles on the filesystem in git as .edn, .cljs and .css, or whatever. You can wire up that webservice yourself in a couple lines of code. We have a lot of built in tools that work like this, for example the schema editor, the toolbar, and the hyperfiddle editor itself which is bootstrapped. Generally we prefer to store everything in the database where reasonable, because we can hot edit it and it's a much faster and fun workflow.