You're right. I was wondering how this company is able to collect such data from real users. It's registered in an apartment in Cracow, Poland, a 1-person compa

You're right. I was wondering how this company is able to collect such data from real users. It's registered in an apartment in Cracow, Poland, a 1-person company till last year (here is their company info in polish: http://www.krs-online.com.pl/perfops-sp-z-o-o-krs-10397838.html http://www.krs-online.com.pl/perfops-sp-z-o-o-krs-10397838.h... , still an apartment address) . Now looking at the Network tab in Developer Tools I can see they are running the tests from JS on their site using visitors of cdnperf.com. I can see requests for URLs like /500b-bench.jpg?t=1552402827417 to various domains.