This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The non-standard HTMLCanvasElement.mozOpaque property is a Boolean reflecting the moz-opaque HTML attribute of the <canvas> element. It lets the canvas know whether or not translucency will be a factor. If the canvas knows there's no translucency, painting performance can be optimized.

This has been standardized as setting the alpha option to false when creating a drawing context with HTMLCanvasElement.getContext(). Use of mozOpaque should be avoided.


var opaque = canvas.mozOpaque;
canvas.mozOpaque = true;


Given this <canvas> element:

<canvas id="canvas" width="300" height="300" moz-opaque></canvas>

You can get or set the mozOpaque property. For example, you could conditionally set it to true if mimeType == 'image/jpeg', or similar, to gain performance in your application when translucency is not needed.

var canvas = document.getElementById('canvas');
console.log(canvas.mozOpaque); // true
// deactivate it
canvas.mozOpaque = false;


Not part of any standard.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support No No3.5 No No No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support No No No4 No No ?

See also

Document Tags and Contributors

 Contributors to this page: fscholz, Jedipedia, nmve, teoli
 Last updated by: fscholz,