The decoding property of the HTMLImageElement interface represents a hint given to the browser on how it should decode the image.


refStr = imgElem.decoding;
imgElem.decoding = refStr;


A DOMString representing the decoding hint. Possible values are:

  • sync: Decode the image synchronously for atomic presentation with other content.
  • async: Decode the image asynchronously to reduce delay in presenting other content.
  • auto: Default mode, which indicates no preference for the decoding mode. The browser decides what is best for the user.

Usage notes

The decoding property allows you to control whether or not the browser is allowed to try to parallelize loading your image. If doing so would cause problems, you can specify sync to disable asynchronous loading. This can be useful when applied to <img> elements, but may be even more so when used for offscreen image objects.


var img = new Image();
img.decoding = 'sync';
img.src = 'img/logo.png'; 


Specification Status Comment
HTML Living Standard
The definition of 'decoding' in that specification.
Living Standard

Browser compatibility

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ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
decodingChrome Full support 65Edge Full support ‚ȧ79Firefox Full support 63IE No support NoOpera Full support YesSafari Full support 11.1WebView Android Full support 65Chrome Android Full support 65Firefox Android Full support 63Opera Android ? Safari iOS Full support 11.3Samsung Internet Android Full support 9.0


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