SpeechRecognition

Constructor

SpeechRecognition()

Creates a new SpeechRecognition object.

Instance properties

SpeechRecognition also inherits properties from its parent interface, EventTarget.

SpeechRecognition.lang

Returns and sets the language of the current SpeechRecognition. If not specified, this defaults to the HTML lang attribute value, or the user agent's language setting if that isn't set either.

SpeechRecognition.continuous

Controls whether continuous results are returned for each recognition, or only a single result. Defaults to single (false.)

SpeechRecognition.interimResults

Controls whether interim results should be returned (true) or not (false.) Interim results are results that are not yet final (e.g., the SpeechRecognitionResult.isFinal property is false.)

SpeechRecognition.maxAlternatives

Sets the maximum number of SpeechRecognitionAlternatives provided per result. The default value is 1.

SpeechRecognition.phrases

Sets an array of SpeechRecognitionPhrase objects to be used for contextual biasing.

SpeechRecognition.processLocally

Specifies whether speech recognition must be performed locally on the user's device.

Deprecated properties

The concept of grammar has been removed from the Web Speech API. Related features remain in the specification and are still recognized by supporting browsers for backwards compatibility, but they have no effect on speech recognition services.

SpeechRecognition.grammars Deprecated

Returns and sets a collection of SpeechGrammar objects that represent the grammars understood by the current SpeechRecognition.

Static methods

SpeechRecognition.available()

Checks whether the specified languages are available for speech recognition.

SpeechRecognition.install()

Installs the required language packs for on-device speech recognition in the specified languages.

Instance methods

SpeechRecognition also inherits methods from its parent interface, EventTarget.

SpeechRecognition.abort()

Stops the speech recognition service from listening to incoming audio, and doesn't attempt to return a SpeechRecognitionResult.

SpeechRecognition.start()

Starts the speech recognition service to listen for incoming audio (from a microphone or an audio track) and returns the results of that recognition.

SpeechRecognition.stop()

Stops the speech recognition service from listening for incoming audio and attempts to return a SpeechRecognitionResult based on the results captured so far.

Events

Listen to these events using addEventListener() or by assigning an event listener to the oneventname property of this interface.

audiostart

Fired when the user agent has started to capture audio.

audioend

Fired when the user agent has finished capturing audio.

end

Fired when the speech recognition service has disconnected.

error

Fired when a speech recognition error occurs.

nomatch

Fired when the speech recognition service returns a final result with no significant recognition. This may involve some degree of recognition, which doesn't meet or exceed the confidence threshold.

result

Fired when the speech recognition service returns a result — a word or phrase has been positively recognized and this has been communicated back to the app.

soundstart

Fired when any sound — recognizable speech or not — has been detected.

soundend

Fired when any sound — recognizable speech or not — has stopped being detected.

speechstart

Fired when sound that is recognized by the speech recognition service as speech has been detected.

speechend

Fired when speech recognized by the speech recognition service has stopped being detected.

start

Fired when the speech recognition service begins listening for audio to recognize.

Examples

In our Speech color changer example, we create a new SpeechRecognition object instance using the SpeechRecognition() constructor.

After some other values have been defined, we then set it so that the recognition service starts when a button is clicked (see SpeechRecognition.start()). When a result has been successfully recognized, the result event fires, we extract the color that was spoken from the event object, and then set the background color of the <html> element to that color.

const recognition = new SpeechRecognition();
recognition.continuous = false;
recognition.lang = "en-US";
recognition.interimResults = false;
recognition.maxAlternatives = 1;

const diagnostic = document.querySelector(".output");
const bg = document.querySelector("html");
const startBtn = document.querySelector("button");

startBtn.onclick = () => {
  recognition.start();
  console.log("Ready to receive a color command.");
};

recognition.onresult = (event) => {
  const color = event.results[0][0].transcript;
  diagnostic.textContent = `Result received: ${color}`;
  bg.style.backgroundColor = color;
};

Specifications

Browser compatibility

See also

• Web Speech API