HTMX is a lightweight JavaScript library that extends HTML with attributes enabling AJAX requests, WebSocket support, and DOM morphing—all without writing JavaScript. Developers write HTML templates on the server, mark elements with HTMX attributes (hx-get, hx-post, hx-trigger, hx-swap), and HTMX handles request/response cycles and DOM updates. Advanced practitioners integrate HTMX with backend frameworks (Django, FastAPI) to build real-time collaborative apps, chat systems, live dashboards, and multiplayer experiences—with minimal client-side code.