Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

WebSocket

A connection that stays open so a server and a browser can both send messages at any time.

A WebSocket starts as an HTTP request with an Upgrade header, then carries framed messages in both directions over the same TCP connection.