The WebSocket.onopen property is an EventHandler that is called when the WebSocket connection's readyState changes to 1; this indicates that the connection is ready to send and receive data. It is called with an Event.


aWebSocket.onopen = function(event) {
  console.log("WebSocket is open now.");


An EventListener.


Specification Status Comment
HTML Living Standard
The definition of 'WebSocket: onopen' in that specification.
Living Standard Initial definition

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
onopenChrome Full support YesEdge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes


Full support
Full support
Compatibility unknown
Compatibility unknown