Jun 8, 2018

Web tracking by hash of an email address

Email addresses are unique and persistent, and thus the hash of an email address is an excellent tracking identifier. 

A user’s email address will seldom change — clearing cookies, using private browsing mode, or switching devices won’t prevent tracking. The hash of an email address can be used to connect the pieces of an online profile scattered across different browsers, devices, and mobile apps. It can also serve as a link between browsing history profiles before and after cookie clears.