<h1>Tutorial: Google Analytics</h1>


<p>This tutorial demonstrates using Google Analytics to track the usage of your
extension.</p>

<h2 id="toc-requirements">Requirements</h2>
<p>
  This tutorial expects that you have some familiarity writing extensions for
  Google Chrome.  If you need information on how to write an extension, please
  read the <a href="getstarted.html">Getting Started tutorial</a>.
</p>

<p>
  You will also need a <a href="http://www.google.com/analytics">Google
  Analytics account</a> set up to track your extension. Note that when setting
  up the account, you can use any value in the Website's URL field, as your
  extension will not have an URL of its own.
</p>

<p style="text-align: center">
  <img src="{{static}}/images/tut_analytics/screenshot01.png"
       style="width:400px;height:82px;"
       alt="The analytics setup with info for a chrome extension filled out." />
</p>

<h2 id="toc-installing">Installing the tracking code</h2>

<p>
  The standard Google Analytics tracking code snippet fetches a file named
  <code>ga.js</code> from an SSL protected URL if the current page
  was loaded using the <code>https://</code> protocol.  <strong>Chrome
  extensions and applications may <em>only</em> use the SSL-protected version of
  <code>ga.js</code></strong>. Loading <code>ga.js</code> over insecure HTTP is
  disallowed by Chrome's default <a href="contentSecurityPolicy.html">Content
  Security Policy</a>. This, plus the fact that Chrome extensions are hosted
  under the <code>chrome-extension://</code> schema, requires a slight
  modification to the usual tracking snippet to pull <code>ga.js</code> directly
  from <code>https://ssl.google-analytics.com/ga.js</code> instead of the
  default location.
</p>

<p>
  Below is a modified snippet for the
  <a href="http://code.google.com/apis/analytics/docs/tracking/asyncTracking.html">asynchronous
  tracking API</a> (the modified line is bolded):
</p>

<pre>
(function() {
  var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
  <strong>ga.src = 'https://ssl.google-analytics.com/ga.js';</strong>
  var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
})();
</pre>

<p>
  You'll also need to ensure that your extension has access to load the resource
  by relaxing the default content security policy. The policy definition in your
  <a href="manifest.html"><code>manifest.json</code></a> might look like:
</p>

<pre>{
  ...,
  "content_security_policy": "script-src 'self' https://ssl.google-analytics.com; object-src 'self'",
  ...
}</pre>

<p>
  Here is a popup page (<code>popup.html</code>) which loads the asynchronous
  tracking code via an external JavaScript file (<code>popup.js</code>) and
  tracks a single page view:
</p>

<pre>popup.js:
=========

var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'UA-XXXXXXXX-X']);
_gaq.push(['_trackPageview']);

(function() {
  var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
  ga.src = 'https://ssl.google-analytics.com/ga.js';
  var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
})();

popup.html:
===========
&lt;!DOCTYPE html>
&lt;html>
 &lt;head>
   ...
  &lt;script src="popup.js">&lt;/script>
 &lt;/head>
 &lt;body>
   ...
 &lt;/body>
&lt;/html>
</pre>

<p>
  Keep in mind that the string <code>UA-XXXXXXXX-X</code> should be replaced
  with your own Google Analytics account number.
</p>

<h2 id="toc-tracking-pageviews">Tracking page views</h2>

<p>
  The <code>_gaq.push(['_trackPageview']);</code> code will track a single
  page view.  This code may be used on any page in your extension.  When
  placed on a background page, it will register a view once per browser
  session.  When placed on a popup, it will register a view once every time
  the popup is opened.
</p>

<p>
  By looking at the page view data for each page in your extension, you can
  get an idea of how many times your users interact with your extension per
  browser session:
</p>

<p style="text-align: center">
  <img src="{{static}}/images/tut_analytics/screenshot02.png"
       style="width:300px;height:119px;"
       alt="Analytics view of the top content for a site." />
</p>

<h2 id="toc-debugging">Monitoring analytics requests</h2>

<p>
  To ensure that tracking data from your extension is being sent to Google
  Analytics, you can inspect the pages of your extension in the
  Developer Tools window (see the
  <a href="tut_debugging.html">debugging tutorial</a> for more information).
  As the following figure shows, you should see requests for a file named
  <strong>__utm.gif</strong> if everything is set up correctly.
</p>

<p style="text-align: center">
  <img src="{{static}}/images/tut_analytics/screenshot04.png"
       style="width:683px;height:418px;"
       alt="Developer Tools window showing the __utm.gif request" />
</p>

<h2 id="toc-tracking-events">Tracking events</h2>

<p>
  By configuring event tracking, you can determine which parts of your
  extension your users interact with the most.  For example, if you have
  three buttons users may click:
</p>

<pre>
  &lt;button id='button1'>Button 1&lt;/button>
  &lt;button id='button2'>Button 2&lt;/button>
  &lt;button id='button3'>Button 3&lt;/button>
</pre>

<p>
  Write a function that sends click events to Google Analytics:
</p>

<pre>
  function trackButton(e) {
    _gaq.push(['_trackEvent', e.target.id, 'clicked']);
  };
</pre>

<p>
  And use it as an event handler for each button's click:
</p>

<pre>
  var buttons = document.querySelectorAll('button');
  for (var i = 0; i < buttons.length; i++) {
    buttons[i].addEventListener('click', trackButtonClick);
  }
</pre>

<p>
  The Google Analytics event tracking overview page will give you metrics
  regarding how many times each individual button is clicked:
</p>

<p style="text-align: center">
  <img src="{{static}}/images/tut_analytics/screenshot03.png"
       style="width:300px;height:482px;"
       alt="Analytics view of the event tracking data for a site." />
</p>

<p>
  By using this approach, you can see which parts of your extension are
  under-or-overutilized.  This information can help guide decisions about UI
  redesigns or additional functionality to implement.
</p>

<p>
  For more information about using event tracking, see the
  Google Analytics
  <a href="https://developers.google.com/analytics/devguides/collection/gajs/eventTrackerGuide">developer
  documentation</a>.
</p>

<h2 id="toc-samplecode">Sample code</h2>

<p>
  A sample extension that uses these techniques is
  available in the Chromium source tree:
</p>

<blockquote>
  <a href="http://src.chromium.org/viewvc/chrome/trunk/src/chrome/common/extensions/docs/examples/tutorials/analytics/">.../examples/tutorials/analytics/</a>
</blockquote>