Google Analytics is a great service for many reasons, not the least of which is its price tag of zero. Another of its great advantages is that site owners just have to follow a few simple steps before being able to track most--but not all--visitors to their site. After signing up for an account and adding a small snippet of code to every page, site owners are ready to track a wealth of information.
But not every visitor can be tracked, and not all types of interaction can be recorded with the basic installation of Google Analytics. And the reasons for both of these limitations are caused by the internal workings of GA itself. Its guts, if you'll excuse the metaphor.
With that in mind, I'm hoping that this post will help demystify what's actually going on in Google Analytics. Specifically, I'm going to focus on how GA collects information from a site's visitors. With a better understanding of this process, you should be able to recognize situations wherein Google Analytics might not be providing your site with very accurate information.
How Does Google Analytics Collect Information About Visitors?
Studies have shown that around 50% of the top million websites on the internet utilize GA. This means that most of the time you are online, your information is being sent to Google's servers. At first, this may seem a little alarming to you; there are obvious privacy concerns when that much information is being collected and passed along when you are browsing the net. Fortunately, Google has taken this concern so seriously that it is built into the very design of GA.
Rather than collecting information about a specific user and tying that to their name, GA instructs its information to be sent anonymously. If I visit a site and check three pages, GA's won't collect information in the form of 'Tim Marco visited your site three times'. Instead, it will simply tell the site that a user, using a specific keyword, browser, and from a certain region, visited their site three times.
Why does any of this matter?
So if for whatever reason you need to have fully accurate information of exactly how many times your site has been accessed, GA is not going to cut the mustard. Or, if you have reason to believe that your site might have an audience that is heavy on either end of the savvy spectrum (either using outdated technology or completely customizing their computers), GA might miss a large segment of your traffic.
If you are concerned that this is the case with your site, you should probably look into a server-log based solution to supplement your site tracking.
The other important takeaway is that because it uses anonymous tracking, GA doesn't allow you to deeply track user-level interaction. For some sites (especially those that require users to sign up and log in), it might be important to know a lot about how individual users traverse from page to page, or how one session differed from another. While you can get some of this information from a default GA setup, it can be much more difficult to track users who, for example, might use a single login from multiple devices.
In such a case, it might be worthwhile to look into a solution such as Piwik.
How important are the limitations of Google Analytics?
All in all, the two limitations I've mentioned aren't really major drawbacks for most sites. There are plenty of reasons why the software is used by half of the world's leading websites.