Node.js + WebSockets: When to Use ws vs socket.io (And Why We Switched)

The Real-Time Dilemma

Our team was building a live sports betting app with 100,000+ concurrent users. We needed real-time updates, but faced a critical choice:

Should we use the minimalist ws library or the feature-packed socket.io?

After 3 months of stress tests, debugging, and rewrites, here’s what we learned—and when each library shines.

1. ws: The Lightweight Powerhouse

✅ Best For:

✔ Raw performance (handles 50K+ connections per server)
✔ Low-level control (you manage reconnections, heartbeats)
✔ No frills needed (just pure WebSockets)

📊 Performance Benchmarks

⚠️ The Catch:

• No auto-reconnect (you implement it)
• No fallback protocols (HTTP long-polling, etc.)
• No rooms/broadcasting (build it yourself)

Code Example:

const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', (socket) => {
  socket.send('Welcome!'); // Raw WebSocket API
});

Use Case: We used ws for live score updates (low latency, high volume).

2. socket.io: The Batteries-Included Option

✅ Best For:

✔ Production resilience (auto-reconnect, heartbeats)
✔ Cross-browser support (falls back to HTTP long-polling)
✔ Built-in features (rooms, namespaces, broadcasting)

📊 Feature Comparison

⚠️ The Catch:

• Overhead (~2.5x slower than ws)
• Complexity (more API surface to learn)
• Harder to scale (stateful by design)

Code Example:

const io = require('socket.io')(3000);

io.on('connection', (socket) => {
  socket.join('game-lobby'); // Built-in rooms
  socket.emit('message', 'Hello!'); // High-level API
});

Use Case: We used socket.io for chat features (needed rooms, reliability).

3. Key Decision Factors

4. Hybrid Approach: When We Used Both

For our betting app:

• ws powered real-time odds updates (low latency, high volume).
• socket.io handled chat and notifications (reliability matters).

Result:

• 50% less CPU usage vs. full socket.io
• Zero dropped connections during peak traffic

5. Migration Tips

✔ Start with socket.io if you need features fast.
✔ Switch to ws later for performance-critical paths.
✔ Monitor connection state (both libraries leak memory if misused).

Key Takeaways

🔹 ws = raw speed, socket.io = resilience
🔹 Hybrid architectures work (use both where they excel)
🔹 Always benchmark (we saved 40% CPU by splitting workloads)

Which library are you using? Have you tried switching?

Further Reading

• ws GitHub
• socket.io Scaling Guide