Web Speech API

This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage 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 specification changes.

The Web Speech API enables you to incorporate voice data into web apps. The Web Speech API has two parts: SpeechSynthesis (Text-to-Speech), and SpeechRecognition (Asynchronous Speech Recognition.)

Web Speech Concepts and Usage

The Web Speech API makes web apps able to handle voice data. There are two components to this API:

  • Speech recogition is accessed via the SpeechRecognition interface, which provides the ability to recognize voice context from an audio input (normally via the device's default speech recognition service) and respond appropriately. Generally you'll use the interface's constructor to create a new SpeechRecognition object, which has a number of event handlers available for detecting when speech is input through the device's microphone. The SpeechGrammar interface represents a container for a particular set of grammar that your app should recognise. Grammar is defined using JSpeech Grammar Format (JSGF.)
  • Speech synthesis is accessed via the SpeechSynthesis interface, a text-to-speech component that allows programs to read out their text content (normally via the device's default speech synthesiser.) Different voice types are represented by SpeechSynthesisVoice objects, and different parts of text that you want to be spoken are represented by SpeechSynthesisUtterance objects. You can get these spoken by passing them to the SpeechSynthesis.speak() method.

For more details on using these features, see Using the Web Speech API.

Web Speech API Interfaces

Speech recognition

The controller interface for the recognition service; this also handles the SpeechRecognitionEvent sent from the recognition service.
Represents a single word that has been recognised by the speech recognition service.
Represents error messages from the recognition service.
The event object for the result and nomatch events, and contains all the data associated with an interim or final speech recognition result.
The words or patterns of words that we want the recognition service to recognize.
Represents a list of SpeechGrammar objects.
Represents a single recognition match, which may contain multiple SpeechRecognitionAlternative objects.
Represents a list of SpeechRecognitionResult objects, or a single one if results are being captured in continuous mode.

Speech synthesis

The controller interface for the speech service; this can be used to retrieve information about the synthesis voices available on the device, start and pause speech, and other commands besides.
Contains information about any errors that occur while processing SpeechSynthesisUtterance objects in the speech service.
Contains information about the current state of SpeechSynthesisUtterance objects that have been processed in the speech service.
Represents a speech request. It contains the content the speech service should read and information about how to read it (e.g. language, pitch and volume.)
Represents a voice that the system supports. Every SpeechSynthesisVoice has its own relative speech service including information about language, name and URI.
Specced out as part of a [NoInterfaceObject] interface called SpeechSynthesisGetter, and Implemented by the Window object, the speechSynthesis property provides access to the SpeechSynthesis controller, and therefore the entry point to speech synthesis functionality.


The Web Speech API repo on GitHub contains demos to illustrate speech recognition and synthesis.


Specification Status Comment
Web Speech API Draft Initial definition

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 33[1] 49 (49)[2] No support No support No support
Feature Android Chrome Firefox Mobile (Gecko) Firefox OS IE Phone Opera Mobile Safari Mobile
Basic support ? (Yes)[1] ? 2.5 No support No support No support
  • [1] Speech recognition interfaces are currently prefixed in Chrome, so you'll need to prefix interface names appropriately, e.g. webkitSpeechRecognition; You'll also need to serve your code through a web server for recognition to work. Speech synthesis is fully supported without prefixes.
  • [2] Recognition can be enabled via the media.webspeech.recognition.enable flag in about:config; synthesis is switched on by default. Note that currently only the speech synthesis part is available in Firefox Desktop — the speech recognition part will be available soon, once the required internal permissions are sorted out.

Firefox OS permissions

To use speech recognition in an app, you need to specify the following permissions in your manifest:

"permissions": {
  "audio-capture" : {
    "description" : "Audio capture"
  "speech-recognition" : {
    "description" : "Speech recognition"

You also need a privileged app, so you need to include this as well:

"type": "privileged"

Speech synthesis needs no permissions to be set.

See also


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

API Experimental Landing recognition Reference speech synthesis Web Speech API