http://ssd.iykpqm7jiradoeezzkhj7c4b33g4hbgfwelht2evxxeicbpjy44c7ead.onion/zh-hans/module/what-fingerprinting
It uses your browser or device characteristics against you, since the identifier is a summary of all the characteristics of your browser or device. Fingerprinting can use all sorts of seemingly mundane details about your device or browser, such as screen resolution, your time zone, operating system version, remaining battery life, and more.