Under the hood, TestCafe uses a URL-rewriting proxy. This proxy injects the driver script that emulates user actions right into the tested page.
So, before test running TestCafe starts a local proxy server on your machine (192.168.1.171:52429 - it's an address of this server) and then start a browser. All requests from the browser to a target server go throw this local proxy server. You can read more about our motivations in a related post.
TestCafe doesn't send any info about your test runs to anywhere.All manipulations with the data is performed on your machine only when your run a test on your local browsers.