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This is documentation for the next SDK version. For up-to-date documentation, see the latest version (SDK 51).

Expo Speech

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

Android

iOS

Web

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

Installation

Terminal

- npx expo install expo-speech

If you are installing this in an existing React Native app (bare workflow), start by installing expo in your project. Then, follow the additional instructions as mentioned by library's README under "Installation in bare React Native projects" section.

Usage

Speech

import * as React from 'react';
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

Android

iOS

Web

`Speech.maxSpeechInputLength`

Type: number

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

Methods

Android

iOS

Web

`Speech.getAvailableVoicesAsync()`

Returns list of all available voices.

Returns:

Promise<Voice[]>

List of Voice objects.

Android

iOS

Web

`Speech.isSpeakingAsync()`

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.

Android

iOS

Web

`Speech.pause()`

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

Returns:

Promise<void>

Android

iOS

Web

`Speech.resume()`

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

Returns:

Promise<void>

Android

iOS

Web

`Speech.speak(text, options)`

Name	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

Android

iOS

Web

`Speech.stop()`

Interrupts current speech and deletes all in queue.

Returns:

Promise<void>

Types

Android

iOS

Web

`SpeechEventCallback()`

Name	Type
this	`SpeechSynthesisUtterance`
ev	`SpeechSynthesisEvent`

Android

iOS

Web

`SpeechOptions`

Name	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.
voice (optional)	`string`	Voice identifier.
volume (optional)	`number`	Only for: Web Volume of the voice to speak `text`. A number between `0.0` (muted) and `1.0` (max volume) Default: `1.0`