This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

The onstart property of the SpeechSynthesisUtterance interface represents an event handler that will run when the utterance has begun to be spoken (when the start event fires.)

This occurs when the SpeechSynthesis.speak() method is invoked.


speechSynthesisUtteranceInstance.onstart = function() { ... };


var synth = window.speechSynthesis;

var inputForm = document.querySelector('form');
var inputTxt = document.querySelector('input');
var voiceSelect = document.querySelector('select');

var voices = synth.getVoices();


inputForm.onsubmit = function(event) {

  var utterThis = new SpeechSynthesisUtterance(inputTxt.value);
  var selectedOption = voiceSelect.selectedOptions[0].getAttribute('data-name');
  for(i = 0; i < voices.length ; i++) {
    if(voices[i].name === selectedOption) {
      utterThis.voice = voices[i];


  utterThis.onstart = function(event) {
    console.log('We have started uttering this speech: ' + event.utterance.text);



Specification Status Comment
Web Speech API
The definition of 'onstart' in that specification.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 33 49 (49) No support ? 7
Feature Android Chrome Firefox Mobile (Gecko) Firefox OS IE Phone Opera Mobile Safari Mobile
Basic support (Yes) (Yes) No support 2.0 No support No support 7.1

See also

Document Tags and Contributors

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