Do You Need to Install Anything to Learn to Code Here?
No. Everything runs in the browser tab you already have open, including the code itself.
No installer, no account, and nothing to configure. Every challenge runs inside this page, in a browser Web Worker -- the same sandboxing technique browsers use to run other scripts safely. That worker has fetch, XMLHttpRequest, WebSocket, EventSource, and importScripts deliberately disabled, so the claim that your code never leaves your browser is enforced by the runtime itself, not just stated on a page.
Press Run to see what your code does.
Press Run above and that line appears without a network request going anywhere -- open your browser's developer tools if you want to check. That also means there is nothing to keep updated on your end and nothing that stops working because a server somewhere is down. The only thing you need is the browser you're reading this in.
Everything above runs in this page, on your own machine. There is more of it on the practice pages.