I believe it's done with JavaScript. You paste their code snippet into all your pages.
More info at gostats.com
Travis
10:15 am on Apr 24, 2018 (gmt 0)
Since KaylaKim mentions "unique visitors", I guess he or she asks how gostats defines a unique visitor.
Like for example this can be 1 IP = 1 visitor, which, in real life is not like that, since several visitors can share the same IP for all kind of reasons.
Counting of unique visitors can also be done using a cookie, and certainly other ways.
keyplyr
10:23 am on Apr 24, 2018 (gmt 0)
If tagged with an ID parameter through JS, the IP address is irrelevant.
I agree with unique visitors tracking being moot if using IP address alone as the ID.