HTMLCanvasElement: mozOpaque property

Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

Non-standard: 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 value 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.

Note: 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. Firefox will stop supporting it in the future.


A boolean value.


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.

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


Not part of any standard.

Browser compatibility

BCD tables only load in the browser

See also