What Is a WebSocket?

WebSockets let servers push data to clients the moment it changes — no polling, no waiting. Here's how they work, what they're good for, and when to use them.

The web was built around a simple idea: you ask, the server answers. You type a URL, the server sends back a page. You submit a form, the server processes it and responds. That back-and-forth is called the request-response cycle, and it works great for most of what the web does.

But what if you need the server to tell you something — without you asking first?

The Problem With HTTP for Live Updates

Imagine you're building a live sports scoreboard. The score changes every few minutes, and you want users to see it update in real time. With plain HTTP, you have a few options — and none of them are great.

You could refresh the whole page every 30 seconds. Works, but clunky. You could use a technique called polling, where your JavaScript sends a request every second asking "anything new?" — but that means a lot of wasted requests when nothing has changed, and still a delay between the update and the user seeing it. There's also a fancier version called long polling, where the server holds the request open until it has something to say, then the client immediately opens another one. It works, but it's awkward to build and puts strain on your servers.

What you really want is a persistent, open channel — something where the server can say "hey, the score just changed" the instant it happens.

That's exactly what a WebSocket is.

What Is a WebSocket?

A WebSocket is a persistent, two-way connection between a client (usually a browser) and a server. Once it's open, both sides can send messages to each other at any time, without waiting for the other to ask first.

Think of regular HTTP like sending letters — you write one, mail it, wait for a reply, then write another. A WebSocket is more like a phone call. Once you're connected, you can both talk whenever you want, and the call stays open until one of you hangs up.

This makes WebSockets a natural fit for anything that needs to feel genuinely live.

How a WebSocket Connection Starts

A WebSocket connection begins its life as an ordinary HTTP request. The browser sends a request to the server with a special header that says, essentially, "I'd like to upgrade this connection to a WebSocket." If the server supports it, it agrees, and the two sides switch protocols. The connection stays open from that point on.

You don't need to think much about this handshake — it happens automatically. The important thing is that after it completes, you have a persistent channel. No more request-response cycles.

Using a WebSocket in the Browser

The browser has a built-in WebSocket API, so you don't need any libraries to get started. Here's what the basic lifecycle looks like:

// Open a connection
const ws = new WebSocket('wss://your-server.example.com/socket');

// React when the connection is established
ws.onopen = () => {
  console.log('Connected!');
  ws.send('Hello from the browser');
};

// React when a message arrives from the server
ws.onmessage = (event) => {
  console.log('Message from server:', event.data);
};

// React if something goes wrong
ws.onerror = (error) => {
  console.error('WebSocket error:', error);
};

// React when the connection closes
ws.onclose = () => {
  console.log('Connection closed');
};

That's it for the basics. You open a connection, listen for messages, and send messages whenever you need to. The server can push data to you at any point — no polling required.

Note the wss:// prefix — that's the secure version of the WebSocket protocol, the same way https:// is the secure version of HTTP. Always use wss:// in production.

What WebSockets Are Great For

WebSockets shine whenever your app needs data that changes frequently and users need to see those changes immediately.

Chat and messaging — Every message needs to appear for all participants the moment it's sent. WebSockets are the standard approach here.

Live feeds and dashboards — Stock prices, sports scores, server metrics, delivery tracking. Anything where the data changes constantly and stale information has real consequences.

Collaborative tools — Think Google Docs, Figma, or Notion. When one person makes a change, everyone else needs to see it instantly. WebSockets make that possible.

Multiplayer games — Player positions, game state, and events all need to sync across players with minimal delay.

Presence and activity indicators — Showing who's online, who's typing, or who's viewing the same document right now. These small touches make apps feel alive, and they rely on a persistent connection to stay current.

What WebSockets Are NOT Great For

WebSockets aren't the right tool for everything. If your use case fits into standard request-response, HTTP is simpler and often the better choice.

One-time requests — Fetching a user's profile, submitting a form, loading a page. These are naturally request-response interactions. There's no need to keep a connection open for them.

File transfers — Uploading or downloading large files is better handled by HTTP, which has mature support for things like progress tracking, resumable uploads, and CDN delivery.

Infrequent updates — If data changes once an hour, the overhead of maintaining a persistent connection isn't worth it. A simple polling approach or a webhook is a better fit.

The rule of thumb: if the server needs to push data to clients proactively and frequently, use WebSockets. If the client just needs to fetch data on demand, use HTTP.

Scaling WebSockets Is the Hard Part

Opening a WebSocket in the browser is easy. Keeping hundreds of thousands of them open across multiple servers is not.

WebSockets are stateful — a connection is tied to a specific server process. If you want to send a message to a user whose connection is on Server B while you're handling a request on Server A, you need a way to route that message across servers. You also need to handle reconnections gracefully when a server restarts, track which users are connected, and deal with load balancing in a way that doesn't break persistent connections.

This is where managed WebSocket infrastructure comes in. Platforms like Apinator handle the infrastructure layer for you — connection state, cross-server message routing, presence tracking, channel authentication, and scaling — so your application code can focus on what to do with messages, not on the mechanics of keeping connections alive across a distributed system.

The Short Version

WebSockets solve the problem of getting live data from a server without constantly asking for it. A WebSocket is a persistent, two-way connection — once it's open, the server can push data to the client at any time. The browser API is simple: open a connection, listen for messages with onmessage, send messages with ws.send().

They're the right choice for chat, live dashboards, collaborative editing, games, and presence features. They're not the right choice for occasional data fetching or file transfers.

And if you're building something that needs WebSockets at scale, the hard part isn't writing the client code — it's the infrastructure underneath. That's a problem worth not solving yourself.

All posts