SSE vs. WebSockets
While both deliver real-time data, they serve different needs:
| Feature | Server-Sent Events (SSE) | WebSockets |
|---|---|---|
| Direction | One-way (Server to Client) | Two-way (Client & Server) |
| Protocol | Runs on standard HTTP/HTTPS | Requires a specialized protocol (ws://) |
| Setup | Extremely simple(built-in EventSource Web API) | More complex (requires handshakes) |
| Data Type | Text only | Text or Binary |
| Best For | Streams, feeds, and notifications | Games, chats, and multiplayer apps |
Browser SSE (Server-Sent Events) is a built-in web technology that allows a server to push real-time updates to a browser over a single, long-lived HTTP connection. Enabling the server to stream data instantly whenever it happens. Typical use cases:
- Live dashboards, stock tickers, or news feeds
- Progress bars or live notifications (e.g., "processing... 10%... 50%")
- Real-time AI response generation (e.g., ChatGPT-style text streaming)
Summary
- SSE is read-only over the persistent connection: The open pipe only flows from server to browser. If the browser wants to "write" (send data), it must bypass the SSE connection and make a separate, standard HTTP request (like a POST or PUT fetch call).
- WebSockets are read and write over the same connection: The single open pipe allows data to flow back and forth simultaneously.