Wouldn’t it be nice to know if the visits to your site are merely repeat visits from the same small group of users (who for example have your home page set as their web browser home page?!) or a broad growing base of users? This is where the Unique Visitors statistic comes into play.
Unique visitors are uniquely identified users who have made web server request (log analysis) or viewed pages (page tagging) within a specified period of time (commonly looked at on a monthly basis). A unique visitor can make multiple visits to a site but are still only counted once within the period.
Commonly the identification method is based off of the IP address assigned to the computer used to access the site or cookie found on the computer.
Truly determining unique visitors can be problematic for a number of reasons including:
- Shifting dynamically assigned IP addresses – A specific computer may be reassigned an IP address within the period making it look like an additional unique user when in fact it is the same user
- NAT IP address assignments – In this case many users may be hiding behind one IP address and will appear as one unique visitor within many return visits (WIFI hot spots for example)
- Shared Computers or devices – In the case of a computer that is shared between many people (families, libraries, etc.) multiple visits to the same site by different people will be recorded as multiple visits by the same unique user
- Same User / Multiple devices – This scenario has a bit of a twist. Let’s say a user accesses a website from home, the office and on the road via smart phone. These will all be recorded as unique visitors even though it is the same person.
- Cookies Crumbles – Users can not accept or delete tracing cookies which can further complicate the situation
This statistic can be one of the most important numbers to follow if you are interested in gauging website growth and content penetration.