Server-Sent Events

EventSource / SSE

Server-Sent Events (SSE) stream real-time updates from server to browser over a persistent HTTP connection — simpler than WebSockets for one-way data.

Example

const es = new EventSource("/api/events");
es.onmessage = ({ data }) => {
  const event = JSON.parse(data);
  updateUI(event);
};
es.addEventListener("update", ({ data }) => handleUpdate(JSON.parse(data)));
es.onerror = () => { es.close(); reconnect(); };
// Server sends: data: {"type":"update","payload":...}

JAVASCRIPT

Full Editor

Pro Tip

SSE reconnects automatically on disconnect — no manual reconnection logic needed.

Related Resources

JavaScript Reference

Complete tag & property list

JavaScript How-To Guides

Step-by-step practical guides

JavaScript Exercises

Practice what you've learned