WebSocket vs SSE: Which Realtime Transport?
WebSocket is a full-duplex, bidirectional channel; Server-Sent Events is a simple one-way stream of updates from server to browser over plain HTTP.
WebSocket upgrades a connection to allow both client and server to send messages anytime, ideal for chat, gaming, and collaborative apps. SSE is a lightweight HTTP-based stream where the server pushes events to the client, with automatic reconnection and easy proxy/caching behavior, ideal for notifications and live feeds. WebSocket favors two-way interaction; SSE favors simple one-way push.
| WebSocket | SSE | |
|---|---|---|
| Direction | Bidirectional | Server to client |
| Protocol | ws:// (upgrade) | Plain HTTP |
| Reconnect | Manual | Automatic |
| Browser API | WebSocket | EventSource |
| Best for | Chat, games, collab | Notifications, live feeds |
Use case and infrastructure
Choose WebSocket when clients must send data continuously (chat, multiplayer, live editing). Choose SSE when the server only needs to push updates (dashboards, notifications, progress) and you want simpler infrastructure, native reconnection, and HTTP-friendly proxies. SSE is limited to text and a connection cap on HTTP/1.1.
In CI and deploy
WebSocket needs proxies and load balancers configured for upgrades and sticky sessions; SSE works through standard HTTP infrastructure with less tuning. Smoke-test realtime endpoints in CI. Either deploys from managed runners, where faster runners shorten build and integration tests.
The verdict
Two-way, low-latency interaction like chat or multiplayer: WebSocket. One-way server push like notifications or live dashboards with the simplest infrastructure: SSE. If you only push from server to client, SSE is often the lighter, more proxy-friendly choice.