Here’s a clear comparison of WebSocket, Web Push, and Server-Sent Events (SSE)—with scenarios for when to use each, tailored for experienced developers:
| Feature | WebSocket | Web Push | Server-Sent Events (SSE) |
|---|---|---|---|
| Communication | Full-duplex, bi-directional | One-way, server-to-client push | One-way, server-to-client streaming |
| Connection | Persistent TCP connection | No persistent connection; via push service | Persistent HTTP connection |
| Use Case | Real-time chat, gaming, collaboration tools needing low latency and bidirectional data | Push notifications even when app is closed or backgrounded, re-engagement | Live feeds, stock tickers, notifications when the app is open and connected |
| Resource Usage | High (maintains open socket) | Low (pushes via OS-level services) | Moderate (keeps HTTP connection open) |
| Works if App Closed? | No (requires open app/tab) | Yes | No |
| Browser & Server Support | Widely supported across browsers and backend stacks | Supported on modern browsers, requires HTTPS, service worker | Supported in browsers except IE; easier server-side than WebSockets |
| Complexity | More complex setup and scaling | Moderate setup (certificates, service workers) | Simpler than WebSocket, uses event streams |
| Delivery Guarantee | Best effort, TCP ensures ordering | Reliable via OS services, user permission required | Best effort over HTTP, can reconnect |
When to Use Each
Use WebSocket when:
- You need low-latency bidirectional communication.
- Building chat apps, multiplayer games, or interactive collaboration suites.
- You can handle scale and keep persistent connections open from many clients.
Use Web Push when:
- Users must be notified even if the app is closed or browser is backgrounded.
- You want to engage or re-engage users with important messages like alerts, promotions, or updates.
- You want a battery-friendly, OS-integrated notification system with guaranteed delivery.
Use Server-Sent Events (SSE) when:
- You need unidirectional, real-time streaming from server to client, such as live news, stock prices, feeds, or status updates.
- Clients remain connected and you want a simpler alternative to WebSockets for data push.
- You prefer built-in browser EventSource API without the complexity of WebSockets.
TL;DR
- WebSocket: Interactive, bidirectional communication while app is open.
- Web Push: Reliable notifications even if app is closed.
- SSE: Lightweight, uni-directional real-time updates with open connection.
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