Decision guide
WebSockets vs SSE vs Long Polling vs Webhooks
How should your system push updates in real time?
Side by side
| Criterion | WebSockets | Server-Sent Events | Long polling | Webhooks |
|---|---|---|---|---|
| Direction | Bidirectional | Server → client | Server → client (pull) | Server → server |
| Latency | Lowest | Low | Low–medium | Seconds |
| Reconnect/resume | DIY | Built in (Last-Event-ID) | Cursor-based | Provider retries |
| Infra compatibility | Needs WS support | Plain HTTP | Plain HTTP | Plain HTTP |
| Scaling concern | Connections + fan-out | Connections | Request churn | Delivery queues + retries |
| Auth | Handshake + per-channel | Cookies / tokens | Normal HTTP auth | Signatures |
When to choose each
WebSockets
Persistent bidirectional connection.
Choose when
- Chat, collaboration, games
- Client → server messages at high frequency
Avoid when
- Simple one-way notifications
- Infrastructure without WS support
Server-Sent Events
HTTP response streaming text events with auto-reconnect.
Choose when
- Feeds, progress, dashboards
- LLM token streaming
Avoid when
- Binary data
- Client → server messaging
Long polling
Held HTTP requests that return when data arrives.
Choose when
- Fallback for restrictive networks
- Low-frequency updates
Avoid when
- High-frequency updates at scale
Webhooks
Server-to-server HTTP callbacks.
Choose when
- Integrations with other companies' systems
Avoid when
- Browsers and mobile clients
Verdict
Prefer SSE for one-way UI updates, WebSockets when clients also send frequent messages, long polling as a fallback, and webhooks (plus an events API) for server-to-server integrations. Mobile apps add push notifications for background delivery.
Learn more
- Real-Time APIs
- API Design
- Stream responses with Server-Sent Events (FastAPI)
- Build a WebSocket chat endpoint in FastAPI (FastAPI)
- Scale real-time Socket.IO across instances (Node.js)
- Show live updates over WebSockets (React)