This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for the proper prefixes to use 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 spec changes.
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 API The definition of 'rate' in that specification. |
Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support | 33 | 44 (44) [1] | Not supported | Not supported | Not supported |
Feature | Android | Chrome | Firefox Mobile (Gecko) | Firefox OS | IE Phone | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|---|
Basic support | ? | (Yes) | ? | 2.5 | Not supported | Not supported | Not supported |
- [1] Can be enabled via the
media.webspeech.synth.enabled
flag in about:config.