OK, IIUC I&#x27;d agree that the &quot;entropy&quot; or uniqueness calculation would be misleading if in fact all user agents with a particular string identifier had the same screen resolution.  IOW in that case it&#x27;s redundant information, and therefore would represent only 10 bits of entropy vs. 13.<p>However I imagine keeping track of all correlations of this type would be a big burden for the identifying algorithm.  Perhaps it&#x27;s more practical to sacrifice some accuracy for the sake of expediency.<p>If the goal is determining the probability that this browser is the same browser that previously connected to my server, the estimate just has to be good enough. Additional refinement may simply not have a big enough payoff to make it worth the trouble.<p>Just my view from the sideline...