WorkerGlobalScope: rejectionhandled event

Baseline Widely available

This feature is well established and works across many devices and browser versions. Its been available across browsers since July 2020.

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Note: This feature is only available in Web Workers.

The rejectionhandled event is sent to the script's global scope (typically WorkerGlobalScope) whenever a rejected Promise is handled late, i.e., when a handler is attached to the promise after its rejection had caused an unhandledrejection event.

This can be used in debugging and for general application resiliency, in tandem with the unhandledrejection event, which is sent when a promise is rejected but there is no handler for the rejection at the time.

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("rejectionhandled", (event) => { })

onrejectionhandled = (event) => { }

Event type

A PromiseRejectionEvent. Inherits from Event.

Event PromiseRejectionEvent

Example

You can use the rejectionhandled event to log promises that get rejected to the console, along with the reasons why they were rejected:

self.addEventListener("rejectionhandled", (event) => {
  console.log(`Promise rejected; reason: ${event.reason}`);
});

Specifications

Specification
HTML # handler-workerglobalscope-onrejectionhandled

Browser compatibility

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This page was last modified on Jul 28, 2026 by MDN contributors.

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