Both can make your app real-time, but sometimes, simpler is smarter.

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Introduction

If you’ve ever built a real-time app, a chat, a dashboard, a notification system, or a live tracker, you’ve probably faced this question:

“Should I use WebSockets or Server-Sent Events (SSE)?”

Most developers immediately reach for WebSockets because they sound cooler: “real-time,” “bi-directional,” “persistent connection.”
But here’s the thing: you might not need them.

In many cases, Server-Sent Events are simpler, faster to implement, easier to scale, and more reliable for one-way updates.

In this guide, we’ll go over:

• How SSE works vs WebSockets
• When SSE is the smarter choice
• Real-world examples where it outperforms WebSockets
• Common mistakes and scalability insights

Let’s start with the basics.

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1. The Goal: Real-Time Updates

The web started as request-response: the browser asks, the server replies, and that’s it.

That model doesn’t work when you need:

• Live dashboards that update every few seconds
• Instant push notifications
• Continuous progress or log streaming
• Real-time event tracking

You need push-based communication, where the server can send updates as they happen, not wait for the client to ask again.

There are two main tools for that in modern browsers:

• Server-Sent Events (SSE)
• WebSockets

Let’s quickly recap how they work before deciding when to pick SSE.

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2. What Are Server-Sent Events (SSE)?

Server-Sent Events use a one-way HTTP connection to stream updates from the server to the client.

Once the connection is established, the server can continuously push text messages without closing it.

How It Works

• The client connects using a standard HTTP request.
• The server responds with Content-Type: text/event-stream.
• The connection remains open indefinitely.
• The browser receives messages as events.

Example: Live Feed with SSE

Server (Node.js + Express)

import express from 'express';
const app = express();

app.get('/events', (req, res) => {
  res.setHeader('Content-Type', 'text/event-stream');
  res.setHeader('Cache-Control', 'no-cache');
  res.setHeader('Connection', 'keep-alive');

  const sendEvent = (data) => res.write(`data: ${JSON.stringify(data)}\n\n`);

  const interval = setInterval(() => {
    sendEvent({ time: new Date().toISOString() });
  }, 2000);

  req.on('close', () => clearInterval(interval));
});

app.listen(3000, () => console.log('SSE running on port 3000'));

Client

const source = new EventSource('/events');
source.onmessage = (event) => console.log('Update:', event.data);

✅ Simple.
✅ Auto-reconnects on failure.
✅ Uses standard HTTP ports (80/443).

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3. What Are WebSockets?

WebSockets create a two-way (full-duplex) connection between the client and the server.

Both sides can send data freely over a persistent TCP connection.

Example: Chat with WebSockets

Server (Node.js + ws)

import { WebSocketServer } from 'ws';
const wss = new WebSocketServer({ port: 3000 });

wss.on('connection', (socket) => {
  console.log('Client connected');
  socket.send('Welcome!');
  socket.on('message', (msg) => console.log('Message:', msg));
});

Client

const socket = new WebSocket('ws://localhost:3000');
socket.onmessage = (e) => console.log('Server:', e.data);
socket.send('Hello Server!');

✅ Perfect for interactive, two-way communication.
✅ Requires manual reconnection handling.

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4. Core Difference: Direction and Complexity

So if your app doesn’t need two-way communication, SSE is a much simpler and more reliable fit.

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5. When to Choose SSE Over WebSockets

1. When You Only Need Server → Client Updates

If users never send real-time messages back (like in dashboards or logs), WebSockets are overkill.

SSE is lightweight and perfect for these cases:

• Stock price feeds
• Weather widgets
• System status updates
• Notification banners
• Build logs or CI/CD pipelines

Example: Notification Stream

const source = new EventSource('/notifications');
source.onmessage = (e) => showNotification(JSON.parse(e.data));

Simple, reliable, and reconnects automatically.

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2. When You Want Simplicity

WebSockets require managing:

• Connection states
• Heartbeats
• Reconnect logic
• Custom binary protocols

SSE?
Just call new EventSource(url) and start receiving data.
No dependencies, no connection handling, no config headaches.

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3. When You Need to Scale Easily

SSE is built on plain HTTP, so it:

• Works with CDNs (like Cloudflare or Akamai)
• Plays nicely with load balancers
• Requires no custom proxy setup

WebSockets, on the other hand, often require:

• Sticky sessions
• WebSocket-aware reverse proxies
• Stateful servers

If you’re deploying on AWS ALB, NGINX, or Kubernetes, SSE will save you pain and setup time.

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4. When You Care About Reliability

SSE automatically reconnects after temporary network drops; the browser handles it for you.

source.onerror = () => console.log('Reconnecting automatically...');

With WebSockets, you must handle reconnection manually or use a library like Socket.IO.

If reliability and simplicity matter more than raw speed, SSE is your friend.

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5. When Data Is Text-Based and Low Frequency

SSE supports text data only, perfect for JSON updates, logs, or messages.
If your app doesn’t need to push thousands of binary updates per second, SSE is lighter and cleaner.

Examples:

• “User joined” events
• “Order updated” notifications
• “Build complete” status messages

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6. When NOT to Use SSE

SSE isn’t perfect. Avoid it when you need:

• Two-way communication (chat, multiplayer, collaboration)
• Binary or heavy data streaming
• Extremely high message throughput
• Compatibility with very old browsers (IE 11)

In those cases, WebSockets or Socket.IO are better fits.

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7. Performance and Scalability Overview

If you’re broadcasting data to many clients (e.g., 10k+ dashboards), SSE scales more naturally it reuses HTTP infrastructure efficiently.

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8. Real-World Scenarios

If 90% of your communication is server → client, using WebSockets is like using a sledgehammer to hang a picture.

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9. Bonus: Combine Both for Best Results

Some large systems use both:

• SSE for system-wide updates (e.g., “New deployment finished”).
• WebSockets for interactive features (e.g., “User typing…”).

Example:

• GitHub uses SSE for activity feeds.
• Figma uses WebSockets for real-time collaboration.

Nothing stops you from mixing both in the same project; use the right tool for each task.

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Conclusion

You don’t always need WebSockets to make your app real-time.

If your app only needs server → client updates, Server-Sent Events give you:

• Less code
• Simpler setup
• Better scalability
• Automatic reconnect
• Native browser support

WebSockets are still amazing, but they’re meant for two-way, high-frequency interactions.

Start with SSE. Upgrade to WebSockets later if your app outgrows it.

Pro Tip: SSE is the “hidden gem” of real-time web development, modern, lightweight, and surprisingly powerful when used right.

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Call to Action

Have you ever replaced WebSockets with SSE in a project?
Share your experience or lessons learned in the comments and bookmark this post for when you design your next real-time feature.