WebSocketSSEReal-TimeWeb DevelopmentSystem Design
SSE vs WebSocket: A Practical Guide for Real-Time Applications
4 mins read
SSE vs WebSocket: Which Should You Choose for Real-Time Apps?
When building real-time apps like notifications, stock tickers, or chat systems, developers often need to push data from servers to clients. The two most common solutions are Server-Sent Events (SSE) and WebSocket. Let's break down their differences and help you pick the right tool.
1. Key Differences at a Glance
| Feature | SSE | WebSocket |
|---|---|---|
| **Connection** | HTTP-based (one-way) | TCP-based (two-way) |
| **Data Flow** | Server → Client only | Both directions |
| **Protocol** | Works with standard HTTP/1.1 | Requires WebSocket protocol |
| **Browser Support** | Built-in (EventSource API) | Widely supported |
| **Data Types** | Text (UTF-8) only | Text + binary |
| **Auto-Reconnect** | Yes | Requires manual handling |
| **Proxy Friendly** | Works with CDNs/load balancers | Needs special proxy config |
2. SSE: Pros and Cons
👍 Why Use SSE
- Easy setup: Just use the
EventSourceAPI – no extra servers needed. - Works everywhere: Uses regular HTTP, compatible with proxies/CDNs.
- Self-healing: Automatically reconnects if the network drops.
- Lightweight: Great for simple updates (e.g., news feeds, logs).
👎 Limitations
- One-way street: Clients can't send data back (use AJAX for extra requests).
- Browser limits: Most allow only ~6 connections per domain.
- Text-only: No support for images or binary data.
3. WebSocket: Pros and Cons
👍 Why Use WebSocket
- Two-way chat: Perfect for apps needing constant back-and-forth (like chat).
- Fast & versatile: Handles text, files, even video streams.
- Persistent: Once connected, stays open for instant updates.
👎 Challenges
- Proxy headaches: Older proxies might block WebSocket connections.
- No auto-reconnect: You'll need to code this yourself.
- Resource-heavy: Not ideal for battery-sensitive mobile apps.
4. When to Use Which?
| Scenario | SSE | WebSocket |
|---|---|---|
| News/stock updates | ✅ Perfect | 🟡 Overkill |
| Chat apps | ❌ No | ✅ Best choice |
| Server logs | ✅ Great | ❌ Unnecessary |
| Video/live streams | ❌ Can't | ✅ Yes |
| CDN-friendly content | ✅ Works | ❌ Nope |
| Mobile-friendly | ✅ Light | ❌ Heavy |
5. The Bottom Line
Choose SSE if:
- You only need server-to-client updates (e.g., notifications).
- You want automatic reconnections.
- Your app uses text data (like JSON).
Choose WebSocket if:
- You need two-way communication (e.g., chat, games).
- You're sending binary data (files, audio).
- Low latency is critical (e.g., multiplayer games).
Both tools have their place – SSE shines for simple updates, while WebSocket rules for interactive apps. 🚀