Window: transitionstart event

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This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The transitionstart event is fired when a CSS transition has actually started, i.e., after any transition-delay has ended.

Bubbles Yes
Cancelable No
Interface TransitionEvent
Event handler property ontransitionstart

The original target for this event is the Element that had the transition applied. You can listen for this event on the Window interface to handle it in the capture or bubbling phases. For full details on this event please see the page on HTMLElement: transitionstart.

Examples

This code adds a listener to the transitionstart event:

window.addEventListener('transitionstart', () => {
  console.log('Started transitioning');
});

The same, but using the ontransitionstart property instead of addEventListener():

window.ontransitionrun = () => {
  console.log('Started transitioning');
};

See a live example of this event.

Specifications

Specification Status Comment
CSS Transitions
The definition of 'transitionstart' in that specification.
Working Draft Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
transitionstart eventChrome No support NoEdge ? Firefox Full support 53IE ? Opera ? Safari ? WebView Android No support NoChrome Android No support NoFirefox Android Full support 53Opera Android ? Safari iOS ? Samsung Internet Android ?

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown

See also