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.)

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

• Speech recognition 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 recognize. 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 synthesizer.) 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.

SpeechRecognition

The controller interface for the recognition service; this also handles the SpeechRecognitionEvent sent from the recognition service.

SpeechRecognitionAlternative

Represents a single word that has been recognized by the speech recognition service.

SpeechRecognitionErrorEvent

Represents error messages from the recognition service.

SpeechRecognitionEvent

The event object for the result and nomatch events, and contains all the data associated with an interim or final speech recognition result.

SpeechGrammar

The words or patterns of words that we want the recognition service to recognize.

SpeechGrammarList

Represents a list of SpeechGrammar objects.

SpeechRecognitionResult

Represents a single recognition match, which may contain multiple SpeechRecognitionAlternative objects.

SpeechRecognitionResultList

Represents a list of SpeechRecognitionResult objects, or a single one if results are being captured in continuous mode.

SpeechSynthesis

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.

SpeechSynthesisErrorEvent

Contains information about any errors that occur while processing SpeechSynthesisUtterance objects in the speech service.

SpeechSynthesisEvent

Contains information about the current state of SpeechSynthesisUtterance objects that have been processed in the speech service.

SpeechSynthesisUtterance

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.)

SpeechSynthesisVoice

Represents a voice that the system supports. Every SpeechSynthesisVoice has its own relative speech service including information about language, name and URI.

Window.speechSynthesis

Specified 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.

For information on errors reported by the Speech API (for example, "language-not-supported" and "language-unavailable"), see the following documentation:

• error property of the SpeechRecognitionErrorEvent object
• error property of the SpeechSynthesisErrorEvent object

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

• Using the Web Speech API
• SitePoint article
• HTML5Rocks article