What Is Server-Sent Events (SSE)?
Server-Sent Events is a standard that lets a server push a continuous stream of text-based updates to a client over a single, long-lived HTTP connection, usi...
Published October 9, 2026
Server-Sent Events is a standard that lets a server push a continuous stream of text-based updates to a client over a single, long-lived HTTP connection, using a simple built-in browser API.
Why it exists
- Some real-time use cases only need server-to-client updates, never the client sending data back over the same channel
- WebSocket supports full two-way communication but requires more setup than is needed for a purely one-directional stream of updates
How to apply it
- Use SSE for one-directional server-to-client streams, like live notifications, activity feeds, or streaming AI-generated text output
- The browser's built-in EventSource API automatically handles reconnection if the connection drops, without extra code
FAQ
Can SSE send data from client to server?
No — SSE is one-directional (server to client) by design. If the client needs to send data back over the same real-time channel, WebSocket is the appropriate choice instead.