A "public suffix" is a domain name under which Internet users can directly register own names. Browsers and other web clients can use it to * avoid privacy-leaking "supercookies" * avoid privacy-leaking "super domain" certificates (see post from Jeffry Walton) * domain highlighting (parts of the domain) in a user interface * sorting domain lists by site libpsl ... * has built-in PSL data for fast access * allows to load PSL data from files * checks if a given domain is a "public suffix" * provides immediate cookie domain verification * finds the longest public part of a given domain * finds the shortest private part of a given domain * works with international domains (UTF-8 and IDNA2008 Punycode) * is thread-safe * handles IDNA2008 UTS#46