Cookies has played a role in the form on web browsing and serves purposes more than just retaining the browser session. It has been massively used to store information about your system, your personal information and widely used for tracker and advertisement. Earlier 2020, the European Union has taken action into improving privacy of its people by enforcing GDPR, making cookies optional mandatory for websites that will be serving the region. 
In the meantime, Google has been testing a new API to replace Cookies via Federated Learning of Cohorts (FLoC). FLoC uses algorithm to obtain and analyze user behaviour and the data is collected and consists from a thousand people. Advertiser will no longer able to get local data but a collection of data that has been filtered. Advertisers are promised to get 95% return of their investment amount via this technology.
While the intention of such tools can be marketed as a way to improve user privacy and less targeted advertisement, FLoC could also be used in a way to identify user preference which too violates one privacy. Whether how much data is gather and segregated with FLoC, it all depends how much of the source code is open to the public for better transparency of the new system.
