coderef

2D canvas opacityLimited availability

The optional alpha parameter of a 2D canvas's getContext() method sets whether the canvas has an alpha transparency channel. If set to false, then this permits the browser to optimize compositing for an opaque canvas.

Not yet supported in all major browsers — check the table and provide a fallback.

How to use ↓Compare browsers

Browser support

DesktopChrome
1–31Not supported
32+Supportedsince Jan 14, 2014
Current: 155
Edge
12–18Not supported
79+Supportedsince Jan 15, 2020
Current: 154
Firefox
1–29Not supported
30+Supportedsince Jun 10, 2014
Current: 157
Safari
✕Not supportedup to 27
Current: 27
MobileChrome Android
18–31Not supported
32+Supportedsince Jan 15, 2014
Current: 155
Firefox Android
4–29Not supported
30+Supportedsince Jun 10, 2014
Current: 157
Safari iOS
✕Not supportedup to 27
Current: 27

How to use

Not supported in Safari, Safari iOS. Use feature detection below and provide a fallback (or a polyfill) for those browsers.

Example

Full syntax and examples are on MDN — see the links below.

Feature detection

JS · check before using
if ("HTMLCanvasElement" in globalThis && "getContext" in HTMLCanvasElement.prototype) {
  // HTMLCanvasElement.getContext is available
}

Specification