What is Google Analytics

Google Analytics (GA) is a free service offered by Google that generates detailed statistics about the visitors to a website. The product is aimed at marketers as opposed to webmasters and technologists from which the industry of web analytics originally grew. It is the most widely used website statistics service,[1] currently in use at around 57% of the 10,000 most popular websites.[2] Another market share analysis claims that Google Analytics is used at around 49.95% of the top 1,000,000 websites (as currently ranked by Alexa).[3]

GA can track visitors from all referrers, including search engines, display advertising, pay-per-click networks, e-mail marketing and digital collateral such as links within PDF documents.

Integrated with AdWords, users can review online campaigns by tracking landing page quality and conversions (goals). Goals might include sales, lead generation, viewing a specific page, or downloading a particular file. These can also be monetized. By using GA, marketers can determine which ads are performing, and which are not, providing the information to optimise or cull campaigns.

GA's approach is to show high level dashboard-type data for the casual user, and more in-depth data further into the report set. Through the use of GA analysis, poor performing pages can be identified using techniques such as funnel visualization, where visitors came from (referrers), how long they stayed and their geographical position. It also provides more advanced features, including custom visitor segmentation.

Users can officially add up to 50 site profiles. Each profile generally corresponds to one website. It is limited to sites which have a traffic of fewer than 5 million pageviews per month (roughly 2 pageviews per second), unless the site is linked to an AdWords campaign.


Google's service was developed from Urchin Software Corporation's analytics system, Urchin on Demand (Google acquired Urchin Software Corp. in April 2005). The system also brings ideas from Adaptive Path, whose product, Measure Map, was acquired and used in the redesign of Google Analytics in 2006.[5] Google still sells the standalone installable Urchin software through a network of value-added resellers and Urchin is at version 7 as of 6/20/11.

The Google-branded version was rolled out in November 2005 to anyone who wished to sign up. However due to extremely high demand for the service, new sign-ups were suspended only a week later. As capacity was added to the system, Google began using a lottery-type invitation-code model. Prior to August 2006 Google was sending out batches of invitation codes as server availability permitted; since mid-August 2006 the service has been fully available to all users – whether they use Google for advertising or not.


Google Analytics is implemented by including what is known as a "page tag". This is referred to as the Google Analytics Tracking Code (GATC) and is a snippet of JavaScript code that the user adds onto every page of his or her website. This code collects visitor data and sends it to a Google data collection server as part of a request for a web beacon.

To function, 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 in size and is only downloaded once at the start of the visit as it will be cached throughout the session. As all websites that implement GA with the ga.js code are using the same master file from Google, a visitor that has previously visited any other website with this code implemented, will also have the file cached on their machine. The result is that the page overhead of including the GATC on web pages is kept to a minimum.

In addition to transmitting information to a Google server, the GATC sets first party cookies on each visitor's computer. This is used to store anonymous information such as whether the visitor has been to the site before (new or returning visitor), what is the timestamp of the current visit and what was the referrer site or campaign the visitor came from e.g. search engine, keywords, banner or email.


Additionally to the JavaScript-based client-side version, the Google Analytics can also work with websites browsed from mobile phones by using the Google Analytics for Mobile package which contains server-side tracking code for mobile sites using PHP, JSP, ASP.NET, or Perl as their server-side language.

However, many ad filtering programs and extensions (such as Firefox's Adblock and NoScript) can block the GATC. This prevents some traffic and users from being tracked, and leads to holes in the collected data. Also, privacy networks like Tor will mask the user's actual location and present inaccurate geographical data. Some users do not have JavaScript-enabled/capable browsers or turn this feature off. However, these limitations are considered small – affecting only a small percentage of visits.[6]

The largest potential impact on data accuracy comes from users deleting or blocking Google Analytics cookies.[7] Without cookies being set, GA cannot collect data. Any individual web user can block or delete cookies resulting in the data loss of those visits for GA users. Website owners can encourage users not to disable cookies, for example by making visitors more comfortable using the site through posting a privacy policy.

These limitations affect all on-site web analytics tools that collect on-site visitor data using page tags. That is, the small piece of code (usually JavaScript) that acts as a beacon to collect visitor data.

Another limitation of GA for large websites is the use of sampling in the generation of many of its reports. To reduce the load on their servers and to provide users with a relatively quick response for their query, GA limits reports to 500,000 randomly sampled visits at the profile level for its calculations. While margins of error are indicated for the visits metric, margins of error are not provided for any other metrics in the GA reports. For small segments of data, the margin of error can be very large.[8]

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