May 26, 2018

C library to handle the Public Suffix List

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 [1]
  • domain highlighting parts of the domain in a user interface
  • sorting domain lists by site


  • 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 libicu is used by psl2c if installed

[1] http//

WWW https//