The start() method of the AudioBufferSourceNode Interface is used to schedule playback of the audio data contained in the buffer, or to begin playback immediately.


AudioBufferSourceNode.start([when][, offset][, duration]);


when Optional
The time, in seconds, at which the sound should begin to play, in the same time coordinate system used by the AudioContext. If when is less than (AudioContext.currentTime, or if it's 0, the sound begins to play at once. The default value is 0.
offset Optional
An offset, specified as the number of seconds in the same time coordinate system as the AudioContext, to the time within the audio buffer that playback should begin. For example, to start playback halfway through a 10-second audio clip, offset should be 5. The default value, 0, will begin playback at the beginning of the audio buffer, and offsets past the end of the audio which will be played (based on the audio buffer's duration and/or the loopEnd property) are silently clamped to the maximum value allowed. The computation of the offset into the sound is performed using the sound buffer's natural sample rate, rather than the current playback rate, so even if the sound is playing at twice its normal speed, the midway point through a 10-second audio buffer is still 5.
duration Optional
The duration of the sound to be played, specified in seconds. If this parameter isn't specified, the sound plays until it reaches its natural conclusion or is stopped using the stop() method. Using this parameter is functionally identical to calling start(when, offset) and then calling stop(when+duration).

Return value



A negative value was specified for one or more of the three time parameters. Please don't attempt to tamper with the laws of temporal physics.
start() has already been called. You can only call this function once during the lifetime of an AudioBufferSourceNode.


The most simple example just starts the audio buffer playing from the beginning — you don't need to specify any parameters in this case:


The following more complex example will, 1 second from now, start playing 10 seconds worth of sound starting 3 seconds into the audio buffer.

source.start(audioCtx.currentTime + 1,3,10);

For a more complete example showing start() in use, check out our AudioContext.decodeAudioData() example, You can also run the code example live, or view the source.


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

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
startChrome No support 14 — 57Edge No support 12 — 79Firefox Full support 25IE No support NoOpera Full support 15Safari Full support 6WebView Android Full support YesChrome Android Full support 18Firefox Android Full support 26Opera Android Full support 14Safari iOS Full support YesSamsung Internet Android Full support 1.0


Full support  
Full support
No support  
No support

See also