Quickstart: Recognize speech in JavaScript in a browser using the Speech SDK

In this article, you'll learn how to create a website using the JavaScript binding of the Cognitive Services Speech SDK to transcribe speech to text. The application is based on the Speech SDK for JavaScript (Download version 1.5.0).


  • A subscription key for the Speech service. See Try the Speech Services for free.
  • A PC or Mac, with a working microphone.
  • A text editor.
  • A current version of Chrome, Microsoft Edge, or Safari.
  • Optionally, a web server that supports hosting PHP scripts.

Create a new Website folder

Create a new, empty folder. In case you want to host the sample on a web server, make sure that the web server can access the folder.

Unpack the Speech SDK for JavaScript into that folder


By downloading any of the Speech SDK for Azure Cognitive Services components on this page, you acknowledge its license. See the Microsoft Software License Terms for the Speech SDK.

Download the Speech SDK as a .zip package and unpack it into the newly created folder. This results in two files being unpacked, microsoft.cognitiveservices.speech.sdk.bundle.js and microsoft.cognitiveservices.speech.sdk.bundle.js.map. The latter file is optional, and is useful for debugging into the SDK code.

Create an index.html page

Create a new file in the folder, named index.html and open this file with a text editor.

  1. Create the following HTML skeleton:

       <title>Speech SDK JavaScript Quickstart</title>
     <!-- UI code goes here -->
     <!-- SDK reference goes here -->
     <!-- Optional authorization token request goes here -->
     <!-- Sample code goes here -->
  2. Add the following UI code to your file, below the first comment:

    <div id="warning">
      <h1 style="font-weight:500;">Speech Recognition Speech SDK not found (microsoft.cognitiveservices.speech.sdk.bundle.js missing).</h1>
    <div id="content" style="display:none">
      <table width="100%">
          <td><h1 style="font-weight:500;">Microsoft Cognitive Services Speech SDK JavaScript Quickstart</h1></td>
          <td align="right"><a href="https://docs.microsoft.com/azure/cognitive-services/speech-service/get-started" target="_blank">Subscription</a>:</td>
          <td><input id="subscriptionKey" type="text" size="40" value="subscription"></td>
          <td align="right">Region</td>
          <td><input id="serviceRegion" type="text" size="40" value="YourServiceRegion"></td>
          <td><button id="startRecognizeOnceAsyncButton">Start recognition</button></td>
          <td align="right" valign="top">Results</td>
          <td><textarea id="phraseDiv" style="display: inline-block;width:500px;height:200px"></textarea></td>
  3. Add a reference to the Speech SDK

    <!-- Speech SDK reference sdk. -->
    <script src="microsoft.cognitiveservices.speech.sdk.bundle.js"></script>
  4. Wire up handlers for the recognition button, recognition result, and subscription-related fields defined by the UI code:

    <!-- Speech SDK USAGE -->
      // status fields and start button in UI
      var phraseDiv;
      var startRecognizeOnceAsyncButton;
      // subscription key and region for speech services.
      var subscriptionKey, serviceRegion;
      var authorizationToken;
      var SpeechSDK;
      var recognizer;
      document.addEventListener("DOMContentLoaded", function () {
        startRecognizeOnceAsyncButton = document.getElementById("startRecognizeOnceAsyncButton");
        subscriptionKey = document.getElementById("subscriptionKey");
        serviceRegion = document.getElementById("serviceRegion");
        phraseDiv = document.getElementById("phraseDiv");
        startRecognizeOnceAsyncButton.addEventListener("click", function () {
          startRecognizeOnceAsyncButton.disabled = true;
          phraseDiv.innerHTML = "";
          // if we got an authorization token, use the token. Otherwise use the provided subscription key
          var speechConfig;
          if (authorizationToken) {
            speechConfig = SpeechSDK.SpeechConfig.fromAuthorizationToken(authorizationToken, serviceRegion.value);
          } else {
            if (subscriptionKey.value === "" || subscriptionKey.value === "subscription") {
              alert("Please enter your Microsoft Cognitive Services Speech subscription key!");
            speechConfig = SpeechSDK.SpeechConfig.fromSubscription(subscriptionKey.value, serviceRegion.value);
          speechConfig.speechRecognitionLanguage = "en-US";
          var audioConfig  = SpeechSDK.AudioConfig.fromDefaultMicrophoneInput();
          recognizer = new SpeechSDK.SpeechRecognizer(speechConfig, audioConfig);
            function (result) {
              startRecognizeOnceAsyncButton.disabled = false;
              phraseDiv.innerHTML += result.text;
              recognizer = undefined;
            function (err) {
              startRecognizeOnceAsyncButton.disabled = false;
              phraseDiv.innerHTML += err;
              recognizer = undefined;
        if (!!window.SpeechSDK) {
          SpeechSDK = window.SpeechSDK;
          startRecognizeOnceAsyncButton.disabled = false;
          document.getElementById('content').style.display = 'block';
          document.getElementById('warning').style.display = 'none';
          // in case we have a function for getting an authorization token, call it.
          if (typeof RequestAuthorizationToken === "function") {

Create the token source (optional)

In case you want to host the web page on a web server, you can optionally provide a token source for your demo application. That way, your subscription key will never leave your server while allowing users to use speech capabilities without entering any authorization code themselves.

  1. Create a new file named token.php. In this example we assume your web server supports the PHP scripting language. Enter the following code:

    header('Access-Control-Allow-Origin: ' . $_SERVER['SERVER_NAME']);
    // Replace with your own subscription key and service region (e.g., "westus").
    $subscriptionKey = 'YourSubscriptionKey';
    $region = 'YourServiceRegion';
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, 'https://' . $region . '.api.cognitive.microsoft.com/sts/v1.0/issueToken');
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_POSTFIELDS, '{}');
    curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json', 'Ocp-Apim-Subscription-Key: ' . $subscriptionKey)); 
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    echo curl_exec($ch);
  2. Edit the index.html file and add the following code to your file:

    <!-- Speech SDK Authorization token -->
    // Note: Replace the URL with a valid endpoint to retrieve
    //       authorization tokens for your subscription.
    var authorizationEndpoint = "token.php";
    function RequestAuthorizationToken() {
      if (authorizationEndpoint) {
        var a = new XMLHttpRequest();
        a.open("GET", authorizationEndpoint);
        a.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
        a.onload = function() {
            var token = JSON.parse(atob(this.responseText.split(".")[1]));
            serviceRegion.value = token.region;
            authorizationToken = this.responseText;
            subscriptionKey.disabled = true;
            subscriptionKey.value = "using authorization token (hit F5 to refresh)";
            console.log("Got an authorization token: " + token);


Authorization tokens only have a limited lifetime. This simplified example does not show how to refresh authorization tokens automatically. As a user, you can manually reload the page or hit F5 to refresh.

Build and run the sample locally

To launch the app, double-click on the index.html file or open index.html with your favorite web browser. It will present a simple GUI allowing you to enter your subscription key and region and trigger a recognition using the microphone.


This method doesn't work on the Safari browser. On Safari, the sample web page needs to be hosted on a web server; Safari doesn't allow websites loaded from a local file to use the microphone.

Build and run the sample via a web server

To launch your app, open your favorite web browser and point it to the public URL that you host the folder on, enter your region, and trigger a recognition using the microphone. If configured, it will acquire a token from your token source.

Next steps