SpeechRecognition.maxAlternatives

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The maxAlternatives property of the SpeechRecognition interface sets the maximum number of SpeechRecognitionAlternatives provided per SpeechRecognitionResult.

The default value is 1.

Syntax

var myMaxAlternativeNumber = mySpeechRecognition.maxAlternatives;
mySpeechRecognition.maxAlternatives = 2;

Value

A number representing the maximum returned alternatives for each result.

Examples

This code is excerpted from our Speech color changer example.

var grammar = '#JSGF V1.0; grammar colors; public <color> = aqua | azure | beige | bisque | black | blue | brown | chocolate | coral | crimson | cyan | fuchsia | ghostwhite | gold | goldenrod | gray | green | indigo | ivory | khaki | lavender | lime | linen | magenta | maroon | moccasin | navy | olive | orange | orchid | peru | pink | plum | purple | red | salmon | sienna | silver | snow | tan | teal | thistle | tomato | turquoise | violet | white | yellow ;'
var recognition = new SpeechRecognition();
var speechRecognitionList = new SpeechGrammarList();
speechRecognitionList.addFromString(grammar, 1);
recognition.grammars = speechRecognitionList;
//recognition.continuous = false;
recognition.lang = 'en-US';
recognition.interimResults = false;
recognition.maxAlternatives = 1;

...

Specifications

Specification	Status	Comment
Web Speech API The definition of 'maxAlternatives' in that specification.	Draft

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`maxAlternatives` Experimental	Chrome Full support 33 Prefixed Notes Full support 33 Prefixed Notes Prefixed Implemented with the vendor prefix: webkit Notes You'll need to serve your code through a web server for recognition to work.	Edge ?	Firefox No support No	IE No support No	Opera No support No	Safari No support No	WebView Android Full support Yes Prefixed Notes Full support Yes Prefixed Notes Prefixed Implemented with the vendor prefix: webkit Notes You'll need to serve your code through a web server for recognition to work.	Chrome Android Full support Yes Prefixed Notes Full support Yes Prefixed Notes Prefixed Implemented with the vendor prefix: webkit Notes You'll need to serve your code through a web server for recognition to work.	Firefox Android No support No	Opera Android No support No	Safari iOS No support No	Samsung Internet Android ?

Legend

Full support: Full support
No support: No support
Compatibility unknown: Compatibility unknown
Experimental. Expect behavior to change in the future.: Experimental. Expect behavior to change in the future.
See implementation notes.: See implementation notes.
Requires a vendor prefix or different name for use.: Requires a vendor prefix or different name for use.

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"