The MediaRecorder.onstartevent handler (part of the MediaRecorder API) handles the start event, allowing you to run code in response to media recording being started by a MediaRecorder.

The start event is thrown as a result of the MediaRecorder.start() method being invoked. At this point, the data starts being gathered into a Blob.


MediaRecorder.onstart = function(event) { ... }
MediaRecorder.addEventListener('start', function(event) { ... })



  record.onclick = function() {
    console.log("recorder started");

  mediaRecorder.onstart = function() {
    // do something in response to
    // recording being started





Specification Status Comment
MediaStream Recording
The definition of 'MediaRecorder.onstart' in that specification.
Working Draft Initial definition

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support471 ?25 ? ? ?
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support ? ? ?25 ? ? ?

1. From version 47: this feature is behind the Experimental Web Platform features preference (needs to be set to Enabled). To change preferences in Chrome, visit chrome://flags.

See also

Document Tags and Contributors

Contributors to this page: lucian95, jpmedley, Sebastianz, chrisdavidmills, teoli, kscarfone
Last updated by: lucian95,