Public Suffix

A public suffix is the part of a website address (domain name) that refers to the highest level of the domain hierarchy, like ".com," ".org," or country codes like ".uk" and ".ca." It defines the boundary between what belongs to the public domain and what is controlled by individual entities, such as websites or organizations. For example, in "example.co.uk," ".uk" is the public suffix, while "co.uk" is a second-level domain. Public suffixes help browsers and browsers services identify how to group websites and manage security, cookies, and policy boundaries across different website parts.