The PromiseRejectionEvent interface represents events which are fired when JavaScript Promises are rejected. These events are particularly useful for telemetry and debugging purposes.


Creates a PromiseRejectionEvent event with the given parameters.


Also inherits properties from its parent Event.

PromiseRejectionEvent.promise Read only
The JavaScript Promise that was rejected.
PromiseRejectionEvent.reason Read only
A value or Object indicating why the promise was rejected, as passed to Promise.reject().


This interface has no unique methods; inherits methods from its parent Event.


Fired when a JavaScript Promise is rejected but there is no rejection handler to deal with the rejection.
Fired when a JavaScript Promise is rejected, and after the rejection is handled by the promise's rejection handling code.


window.onunhandledrejection = function(e) {


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

Browser compatibility

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 49 No support[1] No support No support No support
Feature Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support No support No support[1] No support No support No support

[1] Firefox implements the PromiseRejectionEvent interface if you go to about:config and set the dom.promise_rejection_events.enabled pref to true. However, Firefox doesn't yet actually send the unhandledrejection or understand rejectionhandled events. Completing the implementation will be addressed in bug 1362272.

See also

Document Tags and Contributors

Contributors to this page: Sheppy, chrisdavidmills, fscholz
Last updated by: Sheppy,