Unique visitor tracking in Google Analytics

Until Google’s Universal Analytics is rolled out we have little to no capability in Google Analytics for tracking unique visitors. Here is a little trick to capture “visitors” to your website.

Waiting for Google Universal Analytics

While other digital analytics solutions offer a dedicated visitor ID variable, in Google Analytics (up until now) we have had to use/sacrifice a custom variable out of the 5 variables we’re allowed to use per page.

For all intents and purposes, we’re going to use the following basic Google Analytics tracking code – and don’t get me started on Google Tag Manager and Universal Analytics tagging, I’ll cover those in later posts. Custom variable #1 comes with a visitor scope and a “random” value of “1111-1111-1111-1111” which of course needs to be generated.

<script type="text/javascript">
  var _gaq = _gaq || [];
  _gaq.push(
	['_setAccount', 'UA-XXXXXXX-Y'],
	['_setCustomVar', 1,'Visitor ID', '1111-1111-1111-1111',1],
	['_anonymizeIp'],
	['_trackPageview']
  );

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

A unique visitor number, huh?

Ideally, in this variable, we are going to store a unique identifier. Now, unless the entire population of the planet logs on to your website within the scope of 2 years, we should be safe with slightly-less-than-unique identifiers. You get my drift.

There are 3 ways you can generate a unique identifier:

  • Have the visitor log on to your website and grab their customer/account number and use it in your custom variable. Make sure is cannot personally identify someone, i.e. 1111-1111-1111-1111 should not be traceable to Mr. John Smith without hacking the customer database first.
  • Use Google Analytics’ own cookies by grabbing the value in your __utma cookie.
  • Use Javascript to generate a random series of numbers like that 1111 sequence from earlier but with way random-er numbers.

In this post we’ll focus on the latter case. Here is an example of Javascript unique ID generation code I found on the Interwebs that ties into custom variable generation:

function s4() {
  return Math.floor((1 + Math.random()) * 0x10000).toString(16).substring(1);
};

function guid() {
  return s4() + s4() + '-' + s4() + '-' + s4() + '-' + s4() + '-' + s4() + s4() + s4();
}

var uuid = guid();
_gaq.push(['_setCustomVar', 1,'Visitor ID', uuid,1]);

Note that your _setCustomVar instruction must always take place before a pageview, event or other GA hit type (eCommerce, social, timing, etc).

Install this code, visitors come to your website and receive a unique identifier passed on to the custom variable. You can add more code to handle returning visitors so that they preserve their unique identifier, using cookie as well as the _getVisitorCustomVar instruction to read custom variable values.

How do we use it in reports?

Great question! the easiest way is to build a custom report in explorer mode by using Custom Variable (value 01) as a first dimension. then stack on whatever dimension and metrics combo that you’d like.

Google Analytics unique visitors custom report

The idea is that the first level in this drill-down report is going to be your unique visitor. Of course you’ll have truckloads of visitors to dig through so have fun! Click here for a copy of the custom report builder configuration, in which I present visits by landing page by visitor.

And that’s pretty much it! Google Universal Analytics is going to be visitor-centric so we’ll have use of a dedicated variable for each visitor, using one of the 3 aforementioned methods.

Like this post? Say so in the comments and leave constructive criticism or contact me!

Unique visitor tracking in Google Analytics was last modified: March 5th, 2013 by Julien Coquet

Julien Coquet

Expert de la mesure d’audience sur Internet depuis plus de 15 ans, Julien Coquet est consultant senior digital analytics et responsable produit et évangélisation pour Hub’Scan, une solution d’assurance qualité du marquage analytics.

A propos de Julien Coquet

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One thought on “Unique visitor tracking in Google Analytics

  1. Mehdi

    Google l’autorise? On est où avec l’identification personnelle? Jamais été très clair ce truc.

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