DSC02875 small1Sometimes it is well worth stepping back from the bleeding edge and taking a fresh look at something very familiar, the non-bleeding edge. In this new series I hope to revisit some extremely well established and accepted metrics with the goal of providing fresh insights.

The first one is the metric that is the bedrock of all web analytics: “Visitors”. Almost every metric and report in any web analytics tools either has this metric or is sourced from this metric. It shows up as a raw count or in the shape of percentages or in the numerator or denominator or when we torture it by doing global averages and on and on.

Yet it turns out that there is no standardization and often this metric (count of visitors) masquerades under different names. There is often a misunderstanding as to what it exactly is and how it is measured.

For example the real inspiration for this post is the new tool I am trying out StatCounter. The Summary that greets you in StatCounter shows a graph of “Unique Visitors”. When I probed the support staff at StatCounter as to what this metric was here is how it went: SC: It is based on cookies -> AK: how do you define it? -> SC: It is count of sessions as identified by cookies -> AK: But that is not unique visitors. : )

google analytics visits1Most commonly prevalent names for visitor metrics are: Visitors, Visits, Total Visitors, Unique Visitors, Sessions, Cookies. (Please add the variations you have heard via comments below.)

It is a disservice to the world that so many names exist for the same metric. When we mention visits and unique visitors depending on the tool it is either the same thing or not, it confuses decision makers and sometimes it means that if we rip out Google Analytics and replace it with CoreMetrics we have to unlearn old definitions for the same thing. Quite sub optimal.

Here is a suggested standard, let’s eliminate all complexity and settle on two visitors metrics that anyone can understand on the nine (make that eight : )) planets in our solar system: Total Visitors & Unique Visitors.


  • assumption2If your web analytics platform is still using web logs and your website platform does not use cookies this does not apply to you, specially the Unique Visitor bit. (Though for many reasons you might want to switch to a tag based solution and now with cheap and free ones out there you could consider adding a tag based standard solution.)
  • You are using javascript tag based solutions and you set both persistent (to identify a unique browser, as in IE or firefox etc, with an anonymous id) and transient cookies (to identify as session and its browsing behavior).
  • It is worth diving deep into understanding for your web platform what action starts and terminates the session. For example the start is always the same, someone comes to the site, but session end is not standard. ClickTracks will end your session if you leave the website for a search engine, even if you come back to the same website ten seconds later. Other tools would count it as the same session because you came back in less than 29 minutes.

Metric Definitions: (Updated, thanks Steven)

Total Visitors: Count of all the Sessions during a given time period. (sessions as identified by transient cookie values)

Unique Visitors: Count of all the Unique cookie_id’s during a given time period. (cookie_id’s from persistent cookies)

Most typically Visits, Visitors, Sessions refer to Total Visitors. Cookies is a toss up, refers to both depending on your tool. In StatCounter the value that is called Unique Visitors in reality, per their Support Staff definition, is Total Visitors (sum of sessions).


  • From my humble experience working in a few different companies: People instantly relate to these two metrics without any explanation. Total and Unique Visitors. No vagueness. All other versions if you don’t explain the definition it is impossible to understand what they really are.
  • The benefits of standardization is that independent of the package you use if you call something an apple it will be apple in another package.
  • It will be less confusion for our decision makers when they sit around compare notes with their peers around poker tables. Faster and more confident decisions will result.
  • Above bullet is not just applicable to the Visitor metrics but think about Conversion Rate. It is Outcomes divided by Unique Visitors but for the same site, this blog, if I compute the number using ClickTracks I’ll get one number (in CT unique visitors really is unique visitors) but if I do it using StatCounter I’ll get another number (because in SC unique visitors really is total visitors).
  • There will be world peace (I can't guarantee this of course : )).


  • Vendors: Our dear vendors will have to agree that world peace is important and in some cases relabel the metrics in their reports (for example Google Analytics will change it from Visits to Total Visitors, StatCounter will change the metric from Unique Visitors to Total Visitors etc).
  • Users (You & I): We will dig into our web analytics package today, or call our vendor support rep, and ask them exactly how they define the Visitor metrics. One simple reason, if you get this metric wrong, every thing else you report out is suspect.

While we are on the topic of visitors…….

Two Special Unique Visitor Metric Caveats:

  • badge 2D12I am sure you have heard of all the hype around people loving their cookies and eating them up (or blowing them away if they are on a diet). The Unique Visitor metric is affected by the cookie deletion issue, total visitors is not. The numbers for first party cookies are a 2 – 5% and for third party cookies there is a lot of hot air around what the number is.
    All you need to know” (a nod to Stephen Colbert): 1) Get on first party cookies. 2) Trend it over time and you’ll be fine.
  • Check how your vendor computes Unique Visitors. Your vendor should have the ability to compute uniqueness over the time period you want (atleast for a month). So if you want to know Unique Visitors in August it is the sum of all unique cookie_id’s from Aug first to Aug thirty first. If they compute Unique Visitors as the sum of unique cookie_id’s on Aug first plus Aug second plus Aug third …… plus Aug thirty first, that is not really Unique Visitors.
    All you need to know”: In that case simply use Total Visitor numbers, ignore the Unique Visitor number.

Was the process of revisiting the grand old metric helpful? Are you more confused than ever? Do you agree with the two proposed standard names? Will the vendors switch their naming conventions? Please share your feedback and alternative points of view via comments.

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PS: I want to take a moment and thank the readers of this blog once again for all the kind words and encouragement that you have sent via email and your comments for our daughter Damini. I had mentioned in my Saturday update that she is back home now and we are on our recovery path. Thanks so very much, we are really touched.

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