Unique visitor is a visitor who visited the website at least once in a given period of time. None of his or her subsequent visits to the same website is included in the total of unique visitors which is an important metric indicating the real number of people who came to the webpage at least once in a given period of time.
Why do we need to know the total of unique visitors?
The total of unique visitors is one of the key indicators of the website traffic. It reflects the number of real people having visited a given website at least once in a given period of time (typically a month). Therefore, the total of unique visitors indicates the number of actual visitors (readers) the website has, no matter the frequency of their visit. If we only considered the web traffic, we wouldn’t know the number of real people who have visited the website since the number indicating the web traffic only tells us the number of visits (as opposed to visitors).
How do we find out the number of unique visitors?
The simplest way is making use of unique identifiers recorded in cookies that allow us to know whether the visitor has already visited a given website at some point in the past or not. Thanks to cookies, the user’s web browser can determine whether the visit is unique or recurrent. Naturally, if the user doesn’t allow cookies or the cookies have been deleted from his or her web browser, this piece of information is lost, however, these cases are not statistically significant.