The engine, running in this tab
RustCFML compiled to WebAssembly, executing in your browser. It is the same target that runs on a Cloudflare Worker.
Press Run.The WebAssembly build is about 16 MB and is fetched on your first Run, not on page load. It is the browser target, so there is no filesystem, no datasource and no web server in here. Those need the binary. For a scratchpad that can also run Lucee, Adobe and BoxLang side by side, the community has TryCF.
The same build runs at the edge
What executed your code just now is the WebAssembly target. Put it on a Cloudflare Worker and it serves pages from every location Cloudflare has, with no server to keep alive.
The binary does the rest
Templates, a datasource, sessions, uploads, real OS threads and WebSockets: the parts a browser sandbox cannot offer. One file, no installer.
Then read the docs you know
The compatibility target is cfdocs.org with Lucee as the reference. Most of what you already know about CFML applies unchanged.