When you open a page of this website, the page counts the visit: the page’s address on this site, the name of the website that sent you (for example “google.com”, never the full address you came from), the campaign name a link carried (its utm_source), whether the browser is being driven by a script, and a random visitor number kept in your browser. It is not a cookie. The iPhone app sends none of this.
To leave out robots, our own test runs and our own visits, the website looks at your country and your internet address while the page loads, and stores neither. Visitor numbers are deleted after 30 days; after that only daily totals remain.