Unique visitors are a daily number, and that matters

Ask three analytics products how many unique visitors a site had last week and you will get three answers. That is not incompetence. They are answering different questions.

Where an identifier is deliberately short-lived, “unique visitors” means unique per day. Somebody who came on Monday, Wednesday and Friday is counted three times across the week, once on each day.

This matters when you report upwards. A monthly figure built by adding thirty daily ones will be substantially larger than the number of people who actually visited, and if you present it as “people” once, you are stuck presenting it that way forever.

The honest fix is to say which one you mean every time you quote it. We label ours as daily estimates on the screen itself so nobody has to remember.