SpeechSynthesisUtterance: rate property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2018.

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.

Value

A float representing the rate value. It can range between 0.1 (lowest) and 10 (highest), with 1 being the default rate 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

Adjusting playback rate

In this example we can adjust the playback rate using the slider, then play the utterance with the "Play" button.

HTML

html
<p id="text">It was a dark and stormy night.</p>

<div id="rate-control">
  <label for="rate">Rate:</label>
  <input type="range" min="0.5" max="2" value="1" step="0.1" id="rate" />
</div>

<button id="play">Play</button>

CSS

css
body {
  font-family: sans-serif;
}

#rate-control {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin: 1rem 0;
}

JavaScript

js
const synth = window.speechSynthesis;

const text = document.querySelector("#text");
const play = document.querySelector("#play");
const rate = document.querySelector("#rate");

function speak() {
  if (synth.speaking) {
    synth.cancel();
  }
  const utterThis = new SpeechSynthesisUtterance(text.textContent);
  utterThis.addEventListener("error", () => {
    console.error("SpeechSynthesisUtterance error");
  });
  utterThis.rate = rate.value;
  synth.speak(utterThis);
}

play.addEventListener("click", speak);

Output

Specifications

Specification
Web Speech API
# dom-speechsynthesisutterance-rate

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
rate

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
No support
No support

See also