A unique visitor refers to someone who visits your site for the first time within a specific time-period. However if you look at it in a more detailed manner, a unique visitor is the count of the unique browser cookie or simply called cookie id per user per system/device in conjunction with the system IP address. Any visitor/user who visits your site for the first time would have a cookie dropped into their browser which may last for several months to years and based on this cookie the unique visitor count is captured or identified by the web analytic tool.
We can also look at a rough average of how many visits has been generated based on a single unique visitor, divide total visit by total unique visitors for a certain time period and you get the number.
How does Adobe track unique visitor –
There are few ways to capture the unique visitor. A variable is assigned to capture the visitor ID usually denoted by s.visitorID. The visitor ID can be alpha-numeric or numeric up to 100-character length and must not contain a hypen. If a custom ID is set explicitly then it will be used before the other ID methods.
It is wrong to add up each day’s unique visitors and total it against the month’s unique visitor’s number. The number provided at the end of month (if you are looking at a monthly report) is the consolidated unique figure for that month. There are also few variations of UV like new and returning visitors, total visitors and classification of UV by weekly, daily and monthly
What value does the #unique visitor metric provide to business?
This metric in conjunction with time period (say on a monthly basis) can indicate the quality traffic your site is attracting, you can further see how frequently or often people are coming to you site. This metric coupled with bounce rate can tell, if you are targeting the right audience with the right content. If you are an e-commerce site or a service based company where the goal of your site is to either look at the products sold or newsletter/email signup, then you can divide the total numbers of goals (say a pdf download) achieved by the unique visitors to arrive at the site’s conversion rate.