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Just Exactly What is a Unique Visitor?

What’s the difference between a unique visitor and a user? This post will outline the basics. Many people make the mistake of equating the two, and there are some substantial differences.
First, let’s look at how a web analytics package measures a visitor. The first step is to cookie the machine when a user visits it. Once the cookie is set, that machine is considered a unique visitor.
Whether or not that person is considered a unique visitor the next time they visit a site depends on the time interval being measured. For example, let’s say you had 5,000 unique visitors on Monday, and 4,700 unique visitors on Tuesday. Wee some of Tuesday’s visitors may have visited the site on Monday too. So for Monday and Tuesday together, you may have had only 9,000 unique visitors (because 700 visited both days).
As I said before, a unique visitor does not equate to a unique visit by a human user. It equates to a unique visit by a machine that has not deleted its cookies. Here are the major differences:

  1. More than one human user may be using the same machine. A perfect example of this is a home machine shared by a family. In this case, many people will potentially seem like one unique visitor.
  2. A single human user may use more than one machine. Many people have computers in their office and a different one at home. In this case, a single user will seem like 2 unique visitors.
  3. If a user visits your web site, deletes their cookies, and then comes back, they will look like 2 unique visitors.

One method for getting better data is to require registration. In this event, each human user might have a different account, and more detailed tracking becomes significantly easier. This method is not perfect either, as there are people that share such accounts.
What’s important to remember in analytics is that perfect measurement is not possible. Your goal with an analytics tool needs to be to effectively measure trends and ways to increase business done through your site.
So if your analytics software says that your traffic went from 100,000 unique visitors last month to 150,000 this month, you know you have grown your traffic. While the real numbers might be 110,000 unique visitors last month and 160,000 this month, you can’t worry about that.
There is no way to get better precision, and you have to accept the limitations of the tools. They still provide an awesome resource for growing your business.

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Eric Enge

Eric Enge is part of the Digital Marketing practice at Perficient. He designs studies and produces industry-related research to help prove, debunk, or evolve assumptions about digital marketing practices and their value. Eric is a writer, blogger, researcher, teacher, and keynote speaker and panelist at major industry conferences. Partnering with several other experts, Eric served as the lead author of The Art of SEO.

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