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Reconnecting WebSocket

Build Status Coverage Status

WebSocket that will automatically reconnect if the connection is closed.


  • WebSocket API compatible (same interface, Level0 and Level2 event model)
  • Fully configurable
  • Multi-platform (Web, ServiceWorkers, Node.js, React Native)
  • Dependency free (does not depend on Window, DOM or any EventEmitter library)
  • Handle connection timeouts
  • Allows changing server URL between reconnections
  • Buffering. Will send accumulated messages on open
  • Multiple builds available (see dist folder)
  • Debug mode


npm install --save reconnecting-websocket


Compatible with WebSocket Browser API

So this documentation should be valid: MDN WebSocket API.

Ping me if you find any problems. Or, even better, write a test for your case and make a pull request :)

Simple usage

import ReconnectingWebSocket from 'reconnecting-websocket';

const rws = new ReconnectingWebSocket('ws://');

rws.addEventListener('open', () => {

Update URL

The url parameter will be resolved before connecting, possible types:

  • string
  • () => string
  • () => Promise<string>
import ReconnectingWebSocket from 'reconnecting-websocket';

const urls = ['ws://', 'ws://', 'ws://'];
let urlIndex = 0;

// round robin url provider
const urlProvider = () => urls[urlIndex++ % urls.length];

const rws = new ReconnectingWebSocket(urlProvider);
import ReconnectingWebSocket from 'reconnecting-websocket';

// async url provider
const urlProvider = async () => {
    const token = await getSessionToken();
    return `wss://${token}`;

const rws = new ReconnectingWebSocket(urlProvider);


Sample with custom options

import ReconnectingWebSocket from 'reconnecting-websocket';
import WS from 'ws';

const options = {
    WebSocket: WS, // custom WebSocket constructor
    connectionTimeout: 1000,
    maxRetries: 10,
const rws = new ReconnectingWebSocket('ws://', [], options);

Available options

type Options = {
    WebSocket?: any; // WebSocket constructor, if none provided, defaults to global WebSocket
    maxReconnectionDelay?: number; // max delay in ms between reconnections
    minReconnectionDelay?: number; // min delay in ms between reconnections
    reconnectionDelayGrowFactor?: number; // how fast the reconnection delay grows
    minUptime?: number; // min time in ms to consider connection as stable
    connectionTimeout?: number; // retry connect if not connected after this time, in ms
    maxRetries?: number; // maximum number of retries
    maxEnqueuedMessages?: number; // maximum number of messages to buffer until reconnection
    startClosed?: boolean; // start websocket in CLOSED state, call `.reconnect()` to connect
    debug?: boolean; // enables debug output

Default values

WebSocket: undefined,
maxReconnectionDelay: 10000,
minReconnectionDelay: 1000 + Math.random() * 4000,
reconnectionDelayGrowFactor: 1.3,
minUptime: 5000,
connectionTimeout: 4000,
maxRetries: Infinity,
maxEnqueuedMessages: Infinity,
startClosed: false,
debug: false,



constructor(url: UrlProvider, protocols?: string | string[], options?: Options)

close(code?: number, reason?: string)
reconnect(code?: number, reason?: string)

send(data: string | ArrayBuffer | Blob | ArrayBufferView)

addEventListener(type: 'open' | 'close' | 'message' | 'error', listener: EventListener)
removeEventListener(type:  'open' | 'close' | 'message' | 'error', listener: EventListener)


More info

binaryType: string;
bufferedAmount: number;
extensions: string;
onclose: EventListener;
onerror: EventListener;
onmessage: EventListener;
onopen: EventListener;
protocol: string;
readyState: number;
url: string;
retryCount: number;


CONNECTING 0 The connection is not yet open.
OPEN       1 The connection is open and ready to communicate.
CLOSING    2 The connection is in the process of closing.
CLOSED     3 The connection is closed or couldn't be opened.


Read here