Web Speech API

Speech Recognition in the Browser at SeattleJS

Last month I presented how to take advantage of Speech Recognition in the Browser at SeattleJS meetup. Google Chrome is still the only one browser that supports recognizing speech with WebSpeech API, but since last month Microsoft Edge team has adding WebSpeech API in their backlog. In this session I’m showing how to use the raw, browser API, and also how to easily add voice commands to your website with my voiceCmdr library.

I also would like to mention that SeattleJS is an awesome meetup with great people. I had many interesting conversations at the after-party. If you are from the area I really recommend you to check it out!

Video from my session:

Speech Recognition in the Browser

Last Thursday I had a pleasure to give talk about Speech Recognition in the Browser at the Code Fellows in Seattle.

Many people were surprised how easy it is to add speech recognition to your website with pure JavaScript. So I thought I will share a few code snippets here. It works in Chrome only so far.

Recognizing speech

This is how you can translate speech to text:

var sr = new webkitSpeechRecognition();
sr.onresult = function (evt) {

You can also get the confidence level of the result:

var sr = new webkitSpeechRecognition();
sr.onresult = function (evt) {
    console.log(evt.results[0][0].transcript, evt.results[0][0].confidence);

You can get interim results:

sr.interimResults = true;	// false by default
sr.onresult = function(evt) {
	for (var i = 0; i < evt.results.length; ++i) {

Or different alternatives of recognized speech:

sr.maxAlternatives = 10;	// default = 1
sr.onresult = function(evt) {
	for (var i = 0; i < evt.results[0].length; ++i) {

You can set a language, e.g., to Polish:

sr.lang = 'pl-PL'

All above will stop recognition when you stop speaking. In order to do not stop recognition you need to set continuous flag to true. Additionally, this will treat every fragment of you speech as interim result, so you need to update onresult callback too:

sr.continuous = true;	// false by default
sr.onresult = function(evt) {

Speech Recognition object has other callbacks (than onresult) that you can take advantage of:

sr.onstart = function() { console.log("onstart"); }
sr.onend = function() { console.log("onend"); }
sr.onspeechstart = function() { console.info("speech start"); }
sr.onspeechend = function() { console.info("speech end"); }

Emitting speech

var msg = new SpeechSynthesisUtterance('Hi, I\'m Jakub!');

You can also change the speaker voice:

var voices = window.speechSynthesis.getVoices();
msg.voice = voices[10]; // Note: some voices don't support altering params

There is also other options you can set:

msg.volume = 1; // 0 to 1
msg.pitch = 2; //0 to 2
msg.text = 'Hello World';
msg.lang = 'en-US';

msg.onend = function(e) {
	console.log('Finished in ' + event.elapsedTime + ' seconds.');


Speech is coming to the browser, and you can not stop it. The question is when most of websites will add voice support. Check out voiceCmdr – a library that I blogged about earlier this year, which helps to add voice commands to your websites in very easy way. You can also check out website that can be navigated with voice commands – you can find available commands in my blog post. You can find entire logic for voice commands support in this file (lines: 38-103).

Website with speech recognition for free

A few weeks ago I blogged about voiceCmdr – library for adding voice commands to website (built on top of Web Speech API).

I put up simple website – BooksLib – a books library that allows up voting books, adding to favorites, and searching.

This application enables also voice interaction. You can check it live here (Azure) or here (Heroku).

It works in two modes:

  1. continuous – website is listening for commands continuously
  2. single – website is listening for a single command, and stops listening after receiving

You can enable one of two modes through panel on the top-right corner:

BooksLib - voice panel

Available commands:

  • Home – go to home site
  • Books – go to books site
  • Favorites – go to favorites site
  • Top 10 – go to top 10 site
  • Search [phrase] – search for given phrase (e.g. “Search JavaScript” will display all books with “JavaScript” phrase in title)
  • Favorite – add currently displayed book to favorites (can be used only when single books is displayed)

You can check how these commands were added in lines 60-85, in app.js file (only 25 lines including empty lines and brackets!).

To add voice commands to your website easily check out voiceCmdr library.

* Voice commands works only in Google Chrome – the only web browser that supports Web Speech API so far.