Reference

All functions
apex_domain()	Return the apex/top-private domain from a vector of domains
is_public_suffix()	Test whether a domain is a public suffix
psl	Extract Internet Domain Components Using the Public Suffix List
public_suffix()	Return the public suffix from a vector of domains
suffix_extract()	Separate a domain into component parts
suffix_extract2()	Separate a domain into component parts (urltools compatibility function)