The WebSocket API (WebSockets)

The WebSocket API is an advanced technology that makes it possible to open a two-way interactive communication session between the user's browser and a server. With this API, you can send messages to a server and receive event-driven responses without having to poll the server for a reply.

Note: While a WebSocket connection is functionally somewhat similar to standard Unix-style sockets, they are not related.


The primary interface for connecting to a WebSocket server and then sending and receiving data on the connection.
The event sent by the WebSocket object when the connection closes.
The event sent by the WebSocket object when a message is received from the server.



  • HumbleNet: A cross-platform networking library that works in the browser. It consists of a C wrapper around WebSockets and WebRTC that abstracts away cross-browser differences, facilitating the creation of multi-user networking functionality for games and other apps.
  • µWebSockets: Highly scalable WebSocket server and client implementation for C++11 and Node.js.
  • ClusterWS:  Lightweight, fast and powerful framework for building scalable WebSocket applications in Node.js.
  • CWS: Fast C++ WebSocket implementation for Node.js (uWebSockets v0.14 fork)
  • Socket.IO: A long polling/WebSocket based third party transfer protocol for Node.js.
  • SocketCluster: A pub/sub WebSocket framework for Node.js with a focus on scalability.
  • WebSocket-Node: A WebSocket server API implementation for Node.js.
  • Total.js: Web application framework for Node.js (Example: WebSocket chat)
  • Faye: A WebSocket (two-ways connections) and EventSource (one-way connections) for Node.js Server and Client.
  • SignalR: SignalR will use WebSockets under the covers when it's available, and gracefully fallback to other techniques and technologies when it isn't, while your application code stays the same.
  • Caddy: A web server capable of proxying arbitrary commands (stdin/stdout) as a websocket.
  • ws: a popular WebSocket client & server library for Node.js.
  • jsonrpc-bidirectional: Asynchronous RPC which, on a single connection, may have functions exported on the server and, and the same time, on the client (client may call server, server may also call client).
  • cowboy: Cowboy is a small, fast and modern HTTP server for Erlang/OTP with WebSocket support.
  • WebSocket King: A client tool to help develop, test and work with WebSocket servers.
  • PHP WebSocket Server: Server written in PHP to handle connections via websocksets wss:// or ws://and normal sockets over ssl:// ,tcp://
  • Channels: Django library that adds support for WebSockets (and other protocols that require long running asynchronous connections).


Specification Status Comments
HTML Living Standard
The definition of 'WebSocket API' in that specification.
Living Standard
WebSockets Candidate Recommendation
RFC 6455: The WebSocket Protocol IETF RFC

Browser compatibility

BCD tables only load in the browser

See also