This is documentation for the next SDK version. For up-to-date documentation, see the latest version (SDK 57).

Expo Speech

A library that provides access to text-to-speech functionality.

Android

iOS

Web

Included in Expo Go

GitHub

npm

Changelog

expo-speech provides an API that allows you to utilize Text-to-speech functionality in your app.

On iOS physical devices, expo-speech won't produce sound if the device is in silent mode. Make sure silent mode is turned off.

Installation

Terminal

- npx expo install expo-speech

If you are installing this in an existing React Native app, make sure to install expo in your project.

Usage

Speech

import { View, StyleSheet, Button } from 'react-native';
import * as Speech from 'expo-speech';

export default function App() {
  const speak = () => {
    const thingToSay = '1';
    Speech.speak(thingToSay);
  };

  return (
    <View style={styles.container}>
      <Button title="Press to hear some words" onPress={speak} />
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    backgroundColor: '#ecf0f1',
    padding: 8,
  },
});

API

import * as Speech from 'expo-speech';

Constants

`Speech.maxSpeechInputLength`

Android

iOS

Web

Type: number

Maximum possible text length acceptable by Speech.speak() method. It is platform-dependent. On iOS, this returns Number.MAX_VALUE.

Methods

`Speech.getAvailableVoicesAsync()`

Android

iOS

Web

Returns list of all available voices.

Returns:

Promise<Voice[]>

List of Voice objects.

`Speech.isSpeakingAsync()`

Android

iOS

Web

Determine whether the Text-to-speech utility is currently speaking. Will return true if speaker is paused.

Returns:

Promise<boolean>

Returns a Promise that fulfils with a boolean, true if speaking, false if not.

`Speech.pause()`

iOS, web

Pauses current speech. This method is not available on Android.

Returns:

Promise<void>

`Speech.resume()`

iOS, web

Resumes speaking previously paused speech or does nothing if there's none. This method is not available on Android.

Returns:

Promise<void>

`Speech.speak(text, options)`

Android

iOS

Web

Parameter	Type	Description
text	`string`	The text to be spoken. Cannot be longer than `Speech.maxSpeechInputLength`.
options(optional)	`SpeechOptions`	A `SpeechOptions` object. Default:`{}`

Speak out loud the text given options. Calling this when another text is being spoken adds an utterance to queue.

Returns:

void

`Speech.stop()`

Android

iOS

Web

Interrupts current speech and deletes all in queue.

Returns:

Promise<void>

Types

`SpeechEventCallback(this, ev)`

Android

iOS

Web

Parameter	Type
this	`SpeechSynthesisUtterance`
ev	`SpeechSynthesisEvent`

Returns:

any

`SpeechOptions`

Android

iOS

Web

Property	Type	Description
_voiceIndex(optional)	`number`	-
language(optional)	`string`	The code of a language that should be used to read the `text`, refer to IETF BCP 47 to see valid codes.
onBoundary(optional)	`NativeBoundaryEventCallback \| SpeechEventCallback \| null`	A callback that is invoked when the spoken utterance reaches a word.
onDone(optional)	`() => void \| SpeechEventCallback`	A callback that is invoked when speaking finishes.
onError(optional)	`(error: Error) => void \| SpeechEventCallback`	Only for: Android iOS A callback that is invoked when an error occurred while speaking.
onMark(optional)	`SpeechEventCallback \| null`	-
onPause(optional)	`SpeechEventCallback \| null`	-
onResume(optional)	`SpeechEventCallback \| null`	-
onStart(optional)	`() => void \| SpeechEventCallback`	A callback that is invoked when speaking starts.
onStopped(optional)	`() => void \| SpeechEventCallback`	A callback that is invoked when speaking is stopped by calling `Speech.stop()`.
pitch(optional)	`number`	Pitch of the voice to speak `text`. `1.0` is the normal pitch.
rate(optional)	`number`	Rate of the voice to speak `text`. `1.0` is the normal rate.
useApplicationAudioSession(optional)	`boolean`	Only for: iOS If you set this value to `false`, the system creates a separate audio session to automatically manage speech, interruptions, and mixing and ducking the speech with other audio sources.
voice(optional)	`string`	Voice identifier.
volume(optional)	`number`	Volume of the voice to speak `text`. A number between `0.0` (muted) and `1.0` (max volume) Default:`1.0`

`Voice`

Android

iOS

Web

Object describing the available voices on the device.

Property	Type	Description
identifier	`string`	Voice unique identifier.
language	`string`	Voice language.
name	`string`	Voice name.
quality	`VoiceQuality`	Voice quality.

`WebVoice`

Android

iOS

Web

Type: Voice extended by:

Property	Type	Description
isDefault	`boolean`	-
localService	`boolean`	-
name	`string`	-
voiceURI	`string`	-

Enums

`VoiceQuality`

Android

iOS

Web

Enum representing the voice quality.

`Default`

VoiceQuality.Default ＝ "Default"

`Enhanced`

VoiceQuality.Enhanced ＝ "Enhanced"