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

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Basic supportChrome Full support 47
Notes Disabled
Full support 47
Notes Disabled
Notes Full support since Chrome 49.
Disabled 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.
Edge ? Firefox Full support 25IE ? Opera Full support 36Safari ? WebView Android Full support 49Chrome Android Full support 49Edge Mobile ? Firefox Android Full support 25Opera Android Full support 36Safari iOS ? Samsung Internet Android ?


Full support  
Full support
Compatibility unknown  
Compatibility unknown
See implementation notes.
See implementation notes.
User must explicitly enable this feature.
User must explicitly enable this feature.

See also

Document Tags and Contributors

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