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Monthly Unique Visitors for each Operating System


Level 1


I need to extract the number of Unique Visitors using an app with each Operating System in a given Month. In other words, if user A uses the app with Operating System iOS 14.0 twice in the same month, I want the total for iOS 14.0 to increase ONLY by one.


In order to obtain this result:


  • I created a freeform table
  • I set the time interval to Jan 1, 2021 - Jan 31, 2021
  • I added Unique Visitors as the Metric
  • I added Operating Systems as the Dimesion

The problem is that the total for the Unique Visitors is 1,618,175 while adding up all of the rows related to the different Operating System I get 2,482,990.


I tried to replace the Operating System Dimesion with the Month Dimension: the total for the Unique Visitors remains 1,618,175 and the value for January is exactly the same.


My question is: why there is a 864,815 difference in Unique Visitors between the total for January and total for all the Operating Systems used in January?


Thanks in advance for your answer,



1 Reply


Community Advisor

Unique Visitors, as the metric implies, counts the number of visitors, which for all intents and purposes is the number of people.

It is entirely possible for the same person to be tracked with different operating systems, and people could be updating their OSes regularly (e.g. through automatic updates).

Try including the Visits metric in your table. Do the rows' Visits add up to the total? It is unlikely that a person's OS could update midway while browsing your website.