how is a site able to detect that im not a unique visitor?

[Seamus]

im using a new real ip from my isp and anti detect browser , yet site still detects im not a unique visitor. How is that possible? also tried it with a residential proxy and anti detect browser. Unique visitor means first time visiting site

 

[Watsica I]

Are you using a fresh instance of the browser so there's no cookies?

 

[Prof. Ismael]

You could appear as an outlier in their traffic, it's especially easy to detect if said website doesn't normally get visits. This is irrespective of what data you bring to the table.

Imagine looking at a picture of white noise, you shouldn't be able to distinguish any patterns. But if you start putting black dots in one area, it becomes noticeable very quickly.

You're essentially painting these black dots unless you articulate traffic with respect to the probability constraints.