What is Server-Sent Events (SSE)?

Server-Sent Events provide a standard way for servers to push data to clients over HTTP. Unlike WebSockets (bidirectional), SSE is unidirectional (server to client) but simpler to implement, works over standard HTTP, and automatically reconnects on disconnection. The server sends text/event-stream responses with data, event type, retry interval, and optional IDs for resumption. Use cases include live notifications, stock tickers, social media feeds, and progress updates. SSE works through proxies and load balancers without special configuration. The EventSource JavaScript API provides a clean interface. For bidirectional communication, WebSockets remain the better choice.