Brave Tech World

November 15, 2006

    Definitions:

• Visits: Each new browser session for your site.
• Unique User: Each uniquely identified user that visits your site in a period of time (see my post about how to compute unique users).

    So, happily I went to gather that stats for Sampa, when, suddenly, for one of the websites showed this data for a 24h period:

• Visits: 61
• Unique Users: 63

    What?  How is it possible the site only had 61 visits but 63 unique users in a day?

     Well, it is possible. After a lot of staring at the code, the data and thinking about it, I realize this is perfectly ok, although a bit odd for the untrained eye.

     Here is what happens: A visit is counted as the first time a request comes to the system that causes a new Session to be created. A unique user for a day is counted as the first time a unique id has made a request to the site on that day.

    The key factor: Visits can span multiple days. If somebody visits a site at 11:55 PM and his last request was at 12:15 AM (next day), that means there was 1 visit for day X, 1 unique user for day X and 1 unique user for day X+1.

    In the case of Sampa, we decided to normalize all dates in Universal Time Coordinate (a.k.a. GMT timezone), which means that midnight is 4:00 PM PST.

    Now, for a whole month, that story is different, because that difference will play a much smaller role and become insignificant. Notice that Unique Users (UU) for a month is not the sum of all daily UU, but the true count of unique users that visited that site on that period. On the other hand, Visits for a month is the sum of all the daily visits count.

Comments for "Can Unique Users be greater ...

No comments posted.