HTMLCanvasElement: contextlost event

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

The contextlost event of the Canvas API is fired if the user agent detects that the backing storage associated with a CanvasRenderingContext2D context is lost. Contexts can be lost for several reasons like driver crashes or the application runs out of memory, etc.

By default the user agent will attempt to restore the context and then fire the contextrestored event. User code can prevent the context from being restored by calling Event.preventDefault() during event handling.

Syntax

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

js
addEventListener("contextlost", (event) => {});

oncontextlost = (event) => {};

Event type

A generic Event.

Example

The code fragment below detects the contextlost event.

js
const canvas = document.getElementById("canvas");

canvas.addEventListener("contextlost", (event) => {
  console.log(event);
});

To prevent the context from being restored the code might instead look like this:

js
const canvas = document.getElementById("canvas");

canvas.addEventListener("contextlost", (event) => {
  event.preventDefault();
});

Specifications

Specification
HTML
# event-contextlost

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
contextlost event

Legend

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Full support
Full support
No support
No support

See also