The decodeAudioData() method of the BaseAudioContext Interface is used to asynchronously decode audio file data contained in an ArrayBuffer. In this case the ArrayBuffer is loaded from XMLHttpRequest and FileReader. The decoded AudioBuffer is resampled to the AudioContext's sampling rate, then passed to a callback or promise.

This is the preferred method of creating an audio source for Web Audio API from an audio track. This method only works on complete file data, not fragments of audio file data.


Older callback syntax:

baseAudioContext.decodeAudioData(ArrayBuffer, successCallback, errorCallback);

Newer promise-based syntax:

Promise<decodedData> baseAudioContext.decodeAudioData(ArrayBuffer);


An ArrayBuffer containing the audio data to be decoded, usually grabbed from XMLHttpRequest, WindowOrWorkerGlobalScope.fetch() or FileReader.
A callback function to be invoked when the decoding successfully finishes. The single argument to this callback is an AudioBuffer representing the decodedData (the decoded PCM audio data). Usually you'll want to put the decoded data into an AudioBufferSourceNode, from which it can be played and manipulated how you want.
An optional error callback, to be invoked if an error occurs when the audio data is being decoded.

Return value

Void, or a Promise object that fulfills with the decodedData.


In this section we will first cover the older callback-based system and then the newer promise-based syntax.

Older callback syntax

In this example, the getData() function uses XHR to load an audio track, setting the responseType of the request to arraybuffer so that it returns an array buffer as its response that we then store in the audioData variable . We then pass this buffer into a decodeAudioData() function; the success callback takes the successfully decoded PCM data, puts it into an AudioBufferSourceNode created using AudioContext.createBufferSource(), connects the source to the AudioContext.destination and sets it to loop.

The buttons in the example simply run getData() to load the track and start it playing, and stop it playing, respectively. When the stop() method is called on the source, the source is cleared out.

Note: You can run the example live (or view the source.)

// define variables

var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var source;

var pre = document.querySelector('pre');
var myScript = document.querySelector('script');
var play = document.querySelector('.play');
var stop = document.querySelector('.stop');

// use XHR to load an audio track, and
// decodeAudioData to decode it and stick it in a buffer.
// Then we put the buffer into the source

function getData() {
  source = audioCtx.createBufferSource();
  var request = new XMLHttpRequest();'GET', 'viper.ogg', true);

  request.responseType = 'arraybuffer';

  request.onload = function() {
    var audioData = request.response;

    audioCtx.decodeAudioData(audioData, function(buffer) {
        source.buffer = buffer;

        source.loop = true;

      function(e){ console.log("Error with decoding audio data" + e.err); });



// wire up buttons to stop and play audio

play.onclick = function() {
  play.setAttribute('disabled', 'disabled');

stop.onclick = function() {

// dump script to pre element

pre.innerHTML = myScript.innerHTML;

New promise-based syntax

ctx.decodeAudioData(audioData).then(function(decodedData) {
 // use the decoded data here


Specification Status Comment
Web Audio API
The definition of 'decodeAudioData()' in that specification.
Working Draft

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
decodeAudioDataChrome Full support 10
Full support 10
Prefixed Implemented with the vendor prefix: webkit
Edge Full support YesFirefox Full support 25IE No support NoOpera Full support 22
Full support 22
Full support 15
Prefixed Implemented with the vendor prefix: webkit
Safari Full support 6
Full support 6
Prefixed Implemented with the vendor prefix: webkit
WebView Android Full support YesChrome Android Full support 33Firefox Android Full support 26Opera Android Full support 22
Full support 22
Full support 14
Prefixed Implemented with the vendor prefix: webkit
Safari iOS No support NoSamsung Internet Android Full support Yes
Promise-based syntaxChrome Full support 49Edge ? Firefox Full support 36IE No support NoOpera Full support YesSafari No support NoWebView Android Full support 49Chrome Android Full support 49Firefox Android Full support 36Opera Android ? Safari iOS No support NoSamsung Internet Android ?


Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Requires a vendor prefix or different name for use.
Requires a vendor prefix or different name for use.

See also