Client Installation
The latest release is currently 4.8.0
, released in September 2024.
You can find the release notes here.
Version compatibility
Here is the compatibility table between the server and the JS client:
JS Client version | Socket.IO server version | |||
---|---|---|---|---|
1.x | 2.x | 3.x | 4.x | |
1.x | YES | NO | NO | NO |
2.x | NO | YES | YES1 | YES1 |
3.x | NO | NO | YES | YES |
4.x | NO | NO | YES | YES |
[1] Yes, with allowEIO3: true
Please check the associated migration guides:
Browser support
Socket.IO does support IE9 and above. IE 6/7/8 are not supported anymore.
Browser compatibility is tested thanks to the awesome Sauce Labs platform:
Installation
Standalone build
By default, the Socket.IO server exposes a client bundle at /socket.io/socket.io.js
.
io
will be registered as a global variable:
<script src="/socket.io/socket.io.js"></script>
<script>
const socket = io();
</script>
If you don't need this (see other options below), you can disable the functionality on the server side:
const { Server } = require("socket.io");
const io = new Server({
serveClient: false
});
From a CDN
You can also include the client bundle from a CDN:
<script src="https://cdn.socket.io/4.8.0/socket.io.min.js" integrity="sha384-OoIbkvzsFFQAG88r+IqMAjyOtYDPGO0cqK5HF5Uosdy/zUEGySeAzytENMDynREd" crossorigin="anonymous"></script>
Socket.IO is also available from other CDN:
- cdnjs: https://cdnjs.cloudflare.com/ajax/libs/socket.io/4.8.0/socket.io.min.js
- jsDelivr: https://cdn.jsdelivr.net/npm/socket.io-client@4.8.0/dist/socket.io.min.js
- unpkg: https://unpkg.com/socket.io-client@4.8.0/dist/socket.io.min.js
There are several bundles available:
Name | Size | Description |
---|---|---|
socket.io.js | 34.7 kB gzip | Unminified version, with debug |
socket.io.min.js | 14.7 kB min+gzip | Production version, without debug |
socket.io.msgpack.min.js | 15.3 kB min+gzip | Production version, without debug and with the msgpack parser |
The debug package allows to print debug information to the console. You can find more information here.
During development, we recommend using the socket.io.js
bundle. By setting localStorage.debug = 'socket.io-client:socket'
, any event received by the client will be printed to the console.
For production, please use the socket.io.min.js
bundle, which is an optimized build excluding the debug package.
From NPM
The Socket.IO client is compatible with bundlers like webpack or browserify.
- NPM
- Yarn
- pnpm
npm install socket.io-client
yarn add socket.io-client
pnpm add socket.io-client
The client can also be run from Node.js.
Note: for the reasons cited above, you may want to exclude debug from your browser bundle. With webpack, you can use webpack-remove-debug.
Note for TypeScript users: the types are now included in the socket.io-client
package and thus the types from @types/socket.io-client
are not needed anymore and may in fact cause errors:
Object literal may only specify known properties, and 'extraHeaders' does not exist in type 'ConnectOpts'
Miscellaneous
Dependency tree
A basic installation of the client includes 9 packages, of which 5 are maintained by our team:
└─┬ socket.io-client@4.7.2
├── @socket.io/component-emitter@3.1.0
├─┬ debug@4.3.4
│ └── ms@2.1.2
├─┬ engine.io-client@6.5.2
│ ├── @socket.io/component-emitter@3.1.0 deduped
│ ├── debug@4.3.4 deduped
│ ├── engine.io-parser@5.2.1
│ ├─┬ ws@8.11.0
│ │ ├── UNMET OPTIONAL DEPENDENCY bufferutil@^4.0.1
│ │ └── UNMET OPTIONAL DEPENDENCY utf-8-validate@^5.0.2
│ └── xmlhttprequest-ssl@2.0.0
└─┬ socket.io-parser@4.2.4
├── @socket.io/component-emitter@3.1.0 deduped
└── debug@4.3.4 deduped
Transitive versions
The engine.io-client
package brings the engine that is responsible for managing the low-level connections (HTTP long-polling or WebSocket). See also: How it works
socket.io-client version | engine.io-client version | ws version1 |
---|---|---|
4.7.x | 6.5.x | 8.17.x |
4.6.x | 6.4.x | 8.11.x |
4.5.x | 6.2.x | 8.2.x |
4.4.x | 6.1.x | 8.2.x |
4.3.x | 6.0.x | 8.2.x |
4.2.x | 5.2.x | 7.4.x |
4.1.x | 5.1.x | 7.4.x |
4.0.x | 5.0.x | 7.4.x |
3.1.x | 4.1.x | 7.4.x |
3.0.x | 4.0.x | 7.4.x |
2.5.x | 3.5.x | 7.5.x |
2.4.x | 3.5.x | 7.5.x |
[1] for Node.js users only. In the browser, the native WebSocket API is used.