How is a visitor counted in Piwik PRO?

When a person comes to your website, he or she can be counted as a visitor multiple times.

Piwik PRO uses three mechanisms to recognize a visitor:

  • UserID: a trustworthy ID available on the website or app. Used when the website or app has a mechanism to strictly recognize the visitor, for example, a person provides the ID on his own or logs in. Once set up, the UserID is used as a single source of truth.
  • VisitorID: an ID stored in a cookie set in the visitor’s browser.
  • Visitor's fingerprint: a set of data about the visitor that allows to identify him or her, for example, an IP address, browser type, operating system, and more.

So, when Piwik PRO can recognize a person based on the above information, he will count that person as a visitor. But in some cases, Piwik PRO won’t know that a person is the same visitor.

Here are some of those situations:

  • When a person enters your website on a laptop and mobile, then (unless we use the UserID) he or she will be counted twice.
  • When a person enters your website through different website browsers, then (unless we use the UserID) he or she will be counted multiple times. 
  • When we don’t use UserID or VisitorID, and base on the visitor’s fingerprint, we may count him or her multiple times when they change the location or workstation and the IP address changes.

Another important thing to know is that when you look at reports you may see that the number of visitors doesn’t add up as you would think at first glance.

For example:

  • In week one, we had 2 visitors.
  • In week two, we had 2 the same visitors.

Now when we look at a date range for week one, we’ve got 2 visitors, and for week two 2 visitors as well. But, if we take a date range of these two weeks (week one + week two), we’ve got 2 visitors (not 4 as we might think).

Piwik PRO counts (it’s a predictable counting) the number of visitors for each date range so that you could see the number that corresponds to reality the most.

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