Google Chrome Extensions

Tutorial: Google Analytics

This tutorial demonstrates using Google Analytics to track the usage of your extension.

Requirements

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 Getting Started tutorial.

You will also need a Google Analytics account 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.

The analytics setup with info for a chrome extension filled out.

Installing the tracking code

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

Below is a modified snippet for the asynchronous tracking API (the modified line is bolded): 

(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);
})();

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 manifest.json might look like: 

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

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

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

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

Tracking page views

The _gaq.push(['_trackPageview']); 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.

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:

Analytics view of the top content for a site.

Monitoring analytics requests

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 debugging tutorial for more information). As the following figure shows, you should see requests for a file named __utm.gif if everything is set up correctly.

Developer Tools window showing the __utm.gif request

Tracking events

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: 

  <button id='button1'>Button 1</button>
  <button id='button2'>Button 2</button>
  <button id='button3'>Button 3</button>

Write a function that sends click events to Google Analytics: 

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

And use it as an event handler for each button's click: 

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

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

Analytics view of the event tracking data for a site.

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.

For more information about using event tracking, see the Google Analytics developer documentation.

Sample code

A sample extension that uses these techniques is available in the Chromium source tree:

.../examples/tutorials/analytics/