Do sites using Google Analytics (GA) allow Google to correlate GA traffic with user’s search/gmail/maps/doubleclick/etc traffic?

Google Analytics is a web traffic analysis service offered for free by Google to website owners. The owner of a site merely needs to register with Google and place a snippet of javascript on each web page. Here’s an example of that snippet:

<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
</script>
<script type="text/javascript">
	_uacct = "UA-555555-1";
	urchinTracker();
</script>


As one can see from the above code, a javascript file on google.com is included, the site owner’s identifier (_uacct) is defined and then the urchinTracker() function is called.


This function places four cookies on the end user’s browser. It’s important to note that these are first party cookies, meaning that the domain associated with the GA cookies is the current website and therefore, these cookies can only be read by the current website. This means that if x.com uses GA, and a user visits x.com, and then visits google.com, google can not connect the user’s analytics traffic from x.com with the user’s google.com visit using the unique identifier in the cookie.


That said, Google could connect those two visits with an ip address or ip and user-agent string. This is less reliable that the cookie, but still possible.


These four cookies are:


    

  • __utma

      

    • This cookie expires in year 2038 and contains a long string that looks like this:

        

      • 2252076.984943658.1189608517.1189608517.1189610067.2
        • 

      

      • 

    • The first number (2252076) is a hashed value of the current website’s domain. The second number (984943658) is just a random number. The third, fourth and fifth are timestamps of different events. The third records the date/time that the cookie was first written. The fifth contains the most recent date/time that this cookie was edited (this cookie is written to every time __utmb or __utmc is written, i.e. every 30 minutes or anytime the browser has been closed and reopened). The fourth contains the previous value of the fifth. The sixth value is an integer that records the number of times this cookie has been written.
      • 

    

    • 

  • __utmb

      

    • This cookie expires thirty minutes after last visiting a tracked page for the current website. (This is how GA defines a session.)
      • 

    

    • 

  • __utmc

      

    • This cookie expires when the browser is exited.
      • 

    

    • 

  • __utmz

      

    • This cookie expires in five months (?) and contains another long string that looks something like this:

        

      • 2252076.1189608517.1.1.utmccn=(direct)|utmcrs=(direct)|utmcmd=(none)
        • 

      

      • 

    • The first number is a hashed value of the current website’s domain.
      • 

    • The second number is the timestamp that this cookie was written.
      • 

    • The utm (Urchin Traffic Monitor) fields, utmccn  (click content), utmcsr (click source), utmcmd (click medium), and the optional utmctr (click term), and utmcca (campaign).   Each of these fields can be set by adding HTTP GET parameters, like so:

        

      • http://www.domain.com/

          

        • ?utm_source=sitethelinkison
          • 

        • &utm_medium=organicORcpc
          • 

        • &utm_term=successfulsearchtime
          • 

        • &utm_campaign=AdCampaign
          • 

        • &utm_content=
          • 

        

        • 

      

      • 

    

    • 



If you wish to specifically stop website owners from aggregating details of your use of their website, a good firefox extension is CustomizeGoogle.


Here are some interesting pages about Google Analytics:



Isaac Vetter


Webmaster


Department of Mathematics


Purdue University


www.math.purdue.edu/help