Server-Sent Events
also: SSE
A simple one-way stream: the server pushes a sequence of events to the browser over one long-lived HTTP connection.
Server-Sent Events (SSE) is a lightweight way for a server to push a stream of updates to the browser over one long-lived HTTP connection, one direction only (server to client). The browser’s EventSource API auto-reconnects and resumes.
Worked example: a live notification feed or an LLM streaming its tokens to the UI uses SSE — the server writes events as they happen and the browser receives them without polling. Gotcha: SSE is one-way (for client to server you still need a normal request), text-only, and limited by the browser’s per-domain connection cap on HTTP/1.1 — for true two-way low-latency needs use WebSockets; for simple server-push, SSE is simpler and works over plain HTTP.