The getByteTimeDomainData() method of the AnalyserNode Interface copies the current waveform, or time-domain, data into a Uint8Array (unsigned byte array) passed into it.

If the array has fewer elements than the AnalyserNode.fftSize, excess elements are dropped. If it has more elements than needed, excess elements are ignored.


var audioCtx = new AudioContext();
var analyser = audioCtx.createAnalyser();
var dataArray = new Uint8Array(analyser.fftSize); // Uint8Array should be the same length as the fftSize 
analyser.getByteTimeDomainData(dataArray); // fill the Uint8Array with data returned from getByteTimeDomainData() 


A Uint8Array.


The following example shows basic usage of an AudioContext to create an AnalyserNode, then requestAnimationFrame and <canvas> to collect time domain data repeatedly and draw an "oscilloscope style" output of the current audio input. For more complete applied examples/information, check out our Voice-change-O-matic demo (see app.js lines 128–205 for relevant code).

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


analyser.fftSize = 2048;
var bufferLength = analyser.frequencyBinCount;
var dataArray = new Uint8Array(bufferLength);

// draw an oscilloscope of the current audio source

function draw() {

      drawVisual = requestAnimationFrame(draw);


      canvasCtx.fillStyle = 'rgb(200, 200, 200)';
      canvasCtx.fillRect(0, 0, WIDTH, HEIGHT);

      canvasCtx.lineWidth = 2;
      canvasCtx.strokeStyle = 'rgb(0, 0, 0)';


      var sliceWidth = WIDTH * 1.0 / bufferLength;
      var x = 0;

      for(var i = 0; i < bufferLength; i++) {
        var v = dataArray[i] / 128.0;
        var y = v * HEIGHT/2;

        if(i === 0) {
          canvasCtx.moveTo(x, y);
        } else {
          canvasCtx.lineTo(x, y);

        x += sliceWidth;

      canvasCtx.lineTo(canvas.width, canvas.height/2);



The Uint8Array that the time domain data will be copied to.


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

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 10.0webkit 25.0 (25.0)  No support 15.0webkit
22 (unprefixed)
Feature Android Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support ? 26.0 1.2 ? ? ? 33.0

See also

Document Tags and Contributors

 Contributors to this page: mBut, teoli, chrisdavidmills
 Last updated by: mBut,