The Voice Dictation app uses the Web Speech API to convert your spoken words into text. There’s a simple JavaScript API that lets you integrate Speech Recognition on any website.

The Web Speech API is currently implemented in Chrome and Firefox.

<div>
  <a href="#" id="start_button" onclick="startDictation(event)">Dictate</a>
</div>

<div id="results">
  <span id="final_span" class="final"></span>
  <span id="interim_span" class="interim"></span>
</div>

<script type="text/javascript">
  var final_transcript = '';
  var recognizing = false;

  if ('webkitSpeechRecognition' in window) {
    var recognition = new webkitSpeechRecognition();

    recognition.continuous = true;
    recognition.interimResults = true;

    recognition.onstart = function () {
      recognizing = true;
    };

    recognition.onerror = function (event) {
      console.log(event.error);
    };

    recognition.onend = function () {
      recognizing = false;
    };

    recognition.onresult = function (event) {
      var interim_transcript = '';
      for (var i = event.resultIndex; i < event.results.length; ++i) {
        if (event.results[i].isFinal) {
          final_transcript += event.results[i][0].transcript;
        } else {
          interim_transcript += event.results[i][0].transcript;
        }
      }
      final_transcript = capitalize(final_transcript);
      final_span.innerHTML = linebreak(final_transcript);
      interim_span.innerHTML = linebreak(interim_transcript);
    };
  }

  var two_line = /\n\n/g;
  var one_line = /\n/g;
  function linebreak(s) {
    return s.replace(two_line, '<p></p>').replace(one_line, '<br>');
  }

  function capitalize(s) {
    return s.replace(s.substr(0, 1), function (m) {
      return m.toUpperCase();
    });
  }

  function startDictation(event) {
    if (recognizing) {
      recognition.stop();
      return;
    }
    final_transcript = '';
    recognition.lang = 'en-US';
    recognition.start();
    final_span.innerHTML = '';
    interim_span.innerHTML = '';
  }
</script>