The detail readonly property of the CustomEvent interface returns any data passed when initializing the event.

Note: This feature is available in Web Workers.


 let myDetail = customEventInstance.detail;

Return value

Whatever data the event was initialized with.


// add an appropriate event listener
obj.addEventListener("cat", function(e) { process(e.detail) });

// create and dispatch the event
let event = new CustomEvent("cat", {
  detail: {
    hazcheeseburger: true

// Will return an object contaning the hazcheeseburger property
let myDetail = event.detail;


Specification Status Comment
The definition of 'detail' in that specification.
Living Standard Initial definition.

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
detailChrome Full support 15Edge Full support 14Firefox Full support 11IE No support NoOpera Full support 11.6Safari Full support 6.1WebView Android Full support YesChrome Android Full support YesFirefox Android Full support 14Opera Android Full support YesSafari iOS Full support 6.1Samsung Internet Android Full support Yes


Full support  
Full support
No support  
No support

See also