Best method for calculating duplicates by user's machine?

Question

Web development

Hello everyone
I want to understand what methods are resorted to in order to catch "doubles", 1 participant = 1 device
After all, according to the screen width, browser name and SP, this can not be done
Who implemented it? Does it work?
I’m writing right away, I’m not looking for code, just ideas on how this can

be
implemented