Google Analytics

Google Analytics is implemented with "page tags". A page tag, in this case called the Google Analytics Tracking Code (GATC) is a snippet of JavaScript code that the website owner user adds to every page of the website. The GATC code runs in the client browser when the client browses the page (if JavaScript is enabled in the browser) and collects visitor data and sends it to a Google data collection server as part of a request for a web beacon. The GATC loads a larger Javascript file from the Google webserver and then sets variables with the user's account number. The larger file (currently known as ga.js) is typically 18 KB. The file does not usually have to be loaded, though because of browser caching. Assuming caching is enabled in the browser, it downloads ga.js only once at the start of the visit. Furthermore, as all websites that implement GA with the ga.js code use the same master file from Google, a browser that has previously visited any other website running Google Analytics will already have the file cached on their machine. In addition to transmitting information to a Google server, the GATC sets first party cookies (If cookies are enabled in the browser) on each visitor's computer. These cookies store anonymous information such as whether the visitor has been to the site before (new or returning visitor), the timestamp of the current visit, and the referrer site or campaign that directed the visitor to the page (e.g. search engine, keywords, banner or email).