Public Suffix Service is a Ruby domain name parser based on the Public Suffix
List.

The Public Suffix Service is a cross-vendor initiative to provide an accurate
list of domain name suffixes.

The Public Suffix Service is an initiative of the Mozilla Project, but is
maintained as a community resource. It is available for use in any software, but
was originally created to meet the needs of browser manufacturers.

A "public suffix" is one under which Internet users can directly register names.
Some examples of public suffixes are ".com", ".co.uk" and "pvt.k12.wy.us". The
Public Suffix List is a list of all known public suffixes.

GitHub repository is at https://github.com/weppos/publicsuffix-ruby