SpeechRecognitionAlternative: confidence property

The confidence read-only property of the SpeechRecognitionResult interface returns a numeric estimate of how confident the speech recognition system is that the recognition is correct.

Note: Mozilla's implementation of confidence is still being worked on — at the moment, it always seems to return 1.


A number between 0 and 1.


This code is excerpted from our Speech color changer example.

recognition.onresult = (event) => {
  // The SpeechRecognitionEvent results property returns a SpeechRecognitionResultList object
  // The SpeechRecognitionResultList object contains SpeechRecognitionResult objects.
  // It has a getter so it can be accessed like an array
  // The first [0] returns the SpeechRecognitionResult at position 0.
  // Each SpeechRecognitionResult object contains SpeechRecognitionAlternative objects
  // that contain individual results.
  // These also have getters so they can be accessed like arrays.
  // The second [0] returns the SpeechRecognitionAlternative at position 0.
  // We then return the transcript property of the SpeechRecognitionAlternative object
  const color = event.results[0][0].transcript;
  diagnostic.textContent = `Result received: ${color}.`;
  bg.style.backgroundColor = color;
  console.log(`Confidence: ${event.results[0][0].confidence}`);


Web Speech API
# dom-speechrecognitionalternative-confidence

Browser compatibility

BCD tables only load in the browser

See also