How Google Analytics works?

Google Analytics works by the inclusion of a block of JavaScript code on pages in your website. When visitors to your website view a page, this JavaScript code references a JavaScript file which then executes the tracking operation for Analytics. The tracking operation retrieves data about the page request through various means and sends this information to the Analytics server via a list of parameters attached to a single-pixel image request.

The data that Google Analytics uses to provide all the information in your reports comes from these sources:

• The HTTP request of the visitor
  
• Browser/system information
  
• First-party cookies
  

How the Tracking Code Works

In general, the Google Analytics Tracking Code (GATC) retrieves web page data as follows:

1. . A browser requests a web page that contains the tracking code.
   
2. . A JavaScript Array named _gaq is created and tracking commands are pushed onto the array.
   
3. . A <script> element is created and enabled for asynchronous loading (loading in the background).
   
4. . The ga.js tracking code is fetched, with the appropriate protocol automatically detected. Once the code is fetched and loaded, the commands on the _gaq array are executed and the array is transformed into a tracking object. Subsequent tracking calls are made directly to Google Analytics.
   
5. . Loads the script element to the DOM.
   
6. . After the tracking code collects data, the GIF request is sent to the Analytics database for logging and post-processing.
   

The data contained in the GIF request is the data sent to the Google Analytics servers, which then gets processed and ends up in your reports. Here is an example of only a portion of a GIF request:

http://google-analytics.com/__utm.gif?utmwv=4&utmn=769876874&utmhn=example.com&utmcs=ISO-8859-1&utmsr=1280x1024&utmsc=32-bit&utmul=en-us&utmje=1&utmfl=9.0%20%20r115utmcc=__utma%3D97315849.1774621898.1207701397.1207701397.1207701397.1%3B

How GIF Requests Are Classified

A GIF request is sent to the Analytics servers in the following cases and classified according to the table below (Page, Event, Transaction, Item, Var). In each of these cases, the GIF request is identified by type in the utmt parameter. In addition, the type of the request also determines which data is sent to the Analytics servers. For example, transaction and item data is only sent to the Analytics servers when a purchase is made. Visitor, page, and system information is only sent when an event is recorded or when a page loads, and the user-defined value is only sent when the _setVar method is called.



Requests classified as interaction requests will impact the bounce rate calculations for your page or site. Bounce rate is referred to as a single-page visit to your site, but is strictly defined as a single interaction request during a user session. For this reason, a bounce rate for a page is also affected by ecommerce transactions and event tracking requests. This is because these features co-exist with page tracking and, when they are triggered, they result in additional interaction requests to the Analytics servers.

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