Web/API/SpeechSynthesisUtterance/rate

This is an experimental technologyCheck the Browser compatibility table carefully before using this in production.

The rate property of the SpeechSynthesisUtterance interface gets and sets the speed at which the utterance will be spoken at.

If unset, a default value of 1 will be used.

Syntax

var myRate = speechSynthesisUtteranceInstance.rate;
speechSynthesisUtteranceInstance.rate = 1.5;

Value

A float representing the rate value. It can range between 0.1 (lowest) and 10 (highest), with 1 being the default pitch for the current platform or voice, which should correspond to a normal speaking rate. Other values act as a percentage relative to this, so for example 2 is twice as fast, 0.5 is half as fast, etc.

Some speech synthesis engines or voices may constrain the minimum and maximum rates further. If SSML is used, this value will be overridden by prosody tags in the markup.

Examples

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) {
  event.preventDefault();

  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.rate = 1.5;
  synth.speak(utterThis);
  inputTxt.blur();
}

Specifications

Specification	Status	Comment
Web Speech APIThe definition of 'rate' in that specification.	Draft

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`rate` Experimental'	Chrome Full support 33	Edge Full support 14	Firefox Full support 49	IE No support No	Opera Full support 21	Safari Full support 7	WebView Android No support No	Chrome Android Full support 33	Firefox Android Full support 62 Full support 62 No support 61 — 62 Disabled' Disabled' From version 61 until version 62 (exclusive): this feature is behind the `media.webspeech.synth.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS Full support 7	Samsung Internet Android Full support 3.0

Legend

Full support: Full support
No support: No support
Experimental. Expect behavior to change in the future.': Experimental. Expect behavior to change in the future.
User must explicitly enable this feature.': User must explicitly enable this feature.