Public Suffix List


The Public Suffix List is a catalog of
certain Internet domain names. The term is also known by the form effective top-level domain.
The Mozilla Foundation maintains suffix list for the security and privacy policies of its Firefox web browser, though it is available for other uses under the Mozilla Public License.

List

The list is used by Mozilla browsers, by Google in Chrome and Chromium projects on certain platforms, and by Opera.
According to Mozilla,
While com, uk, and us are top-level domains, Internet users cannot always register the next level of domain, such as "co.uk" or "wy.us", because these may be controlled by domain registrars. By contrast, users can register second level domains within com, such as example.com, because registrars control only the top level. The Public Suffix List is intended to enumerate all domain suffixes controlled by registrars.
Some uses for the list are: