Window: error event

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨July 2015⁩.

Theerror event is fired on aWindow object when a resource failed to load or couldn't be used — for example if a script has an execution error.

This event is only generated for script errors thrown synchronously, such as during initial loading or within event handlers. If a promise was rejected (including an uncaughtthrow within anasync function) and no rejection handlers were attached, anunhandledrejection event is fired instead.

Syntax

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

addEventListener("error", (event) => { })onerror = (message, source, lineno, colno, error) => { }

Note:For historical reasons,onerror onWindow andWorkerGlobalScope objects is the only event handler property that receives more than one argument.

Event type

The event object is anErrorEvent instance if it was generated from a user interface element, or anEvent instance otherwise.

Description

Event handler property

For historical reasons, theonerror event handler property, onWindow andWorkerGlobalScope objects only, has different behavior from other event handler properties.

Note that this only applies to handlers assigned toonerror, not to handlers added usingaddEventListener().

Cancellation

Most event handlers assigned to event handler properties can cancel the event's default behavior by returningfalse from the handler:

textarea.onkeydown = () => false;

However, for an event handler property to cancel the default behavior of theerror event ofWindow, it must instead returntrue:

window.onerror = () => true;

When canceled, the error won't appear in the console, but the current script will still stop executing.

Arguments

The event handler's signature is asymmetric betweenaddEventListener() andonerror. The event handler passed toWindow.addEventListener() receives a singleErrorEvent object, while theonerror handler receives five arguments, matching theErrorEvent object's properties:

message: A string containing a human-readable error message describing the problem. Same asErrorEvent.message.
Note:In HTML, thecontent event handler attributeonerror on the<body> element attacheserror event listeners towindow (not the<body> element). For this event handler, the first parameter is calledevent, notmessage, although it still contains a string; that is, you would use<body onerror="console.error(event)"> to log the error message.
source: A string containing the URL of the script that generated the error.
lineno: An integer containing the line number of the script file on which the error occurred.
colno: An integer containing the column number of the script file on which the error occurred.
error: The error being thrown. Usually anError object.

window.onerror = (a, b, c, d, e) => {  console.log(`message: ${a}`);  console.log(`source: ${b}`);  console.log(`lineno: ${c}`);  console.log(`colno: ${d}`);  console.log(`error: ${e}`);  return true;};

Note:These parameter names are observable with anHTML event handler attribute, where the first parameter is calledevent instead ofmessage.

This special behavior only happens for theonerror event handler onwindow. TheElement.onerror handler still receives a singleErrorEvent object.

Examples

Live example

HTML

html

<div>  <button type="button">Generate script error</button>  <img src="bad-image.jpg" alt="I don't exist" /></div><div>  <label for="eventLog">Event log:</label>  <textarea    readonly       rows="8"    cols="30"   ></textarea></div>

body {  display: grid;  grid-template-areas: "control log";}.controls {  grid-area: control;  display: flex;  align-items: center;  justify-content: center;}.event-log {  grid-area: log;}.event-log-contents {  resize: none;}label,button {  display: block;}button {  height: 2rem;  margin: 0.5rem;}img {  width: 0;  height: 0;}

JavaScript

const log = document.querySelector(".event-log-contents");window.addEventListener("error", (event) => {  log.textContent = `${log.textContent}${event.type}: ${event.message}\n`;  console.log(event);});const scriptError = document.querySelector("#script-error");scriptError.addEventListener("click", () => {  throw new Error("This is a script error");});

Result

Specifications

Specification
HTML # event-error
HTML # handler-onerror

Browser compatibility

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This page was last modified on⁨Nov 3, 2025⁩ byMDN contributors.

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