An OCaml library for parsing and querying the Mozilla Public Suffix List (PSL) to determine public suffixes and registrable domains. This library implements the algorithm specified at publicsuffix.org and provides efficient lookups using a pre-compiled trie data structure.

Key Features#

Complete PSL Support: Handles ICANN and private domain sections
Full Rule Coverage: Supports normal rules, wildcard rules (e.g., *.uk), and exception rules (e.g., !parliament.uk)
Efficient Lookups: Pre-compiled trie structure for fast domain matching
Punycode Support: Automatic handling of internationalized domain names via the punycode library
Type Safety: Uses the domain-name library for validated domain representations

Usage#

(* Determine the registrable domain (public suffix + one label) *)
let domain = Domain_name.of_string_exn "www.example.com" in
match Publicsuffix.registrable_domain domain with
| Some reg_domain -> Format.printf "Registrable: %a\n" Domain_name.pp reg_domain
| None -> Format.printf "No registrable domain\n"
(* Output: Registrable: example.com *)

(* Find the public suffix *)
match Publicsuffix.public_suffix domain with
| Some suffix -> Format.printf "Suffix: %a\n" Domain_name.pp suffix
| None -> Format.printf "No public suffix\n"
(* Output: Suffix: com *)

(* Check if a domain is itself a public suffix *)
let is_suffix = Publicsuffix.is_public_suffix domain in
Format.printf "Is public suffix: %b\n" is_suffix
(* Output: Is public suffix: false *)

For domains with wildcards and exceptions:

(* Example with wildcard rule: *.uk *)
let domain = Domain_name.of_string_exn "example.uk" in
match Publicsuffix.public_suffix domain with
| Some suffix -> Format.printf "Suffix: %a\n" Domain_name.pp suffix
| None -> ()
(* Output: Suffix: uk *)

(* Example with exception rule: !parliament.uk *)
let domain = Domain_name.of_string_exn "parliament.uk" in
match Publicsuffix.registrable_domain domain with
| Some reg_domain -> Format.printf "Registrable: %a\n" Domain_name.pp reg_domain
| None -> ()
(* Output: Registrable: parliament.uk *)

Installation#

opam install publicsuffix

Updating the Public Suffix List Data#

The data/public_suffix_list.dat file contains the PSL data, which is compiled into the library at build time. To update to the latest version:

curl -o data/public_suffix_list.dat https://publicsuffix.org/list/public_suffix_list.dat
opam exec -- dune build

Documentation#

API documentation is available via:

opam install publicsuffix
odig doc publicsuffix

Or build locally:

opam exec -- dune build @doc

Technical Standards#

This library is built on the following Internet standards:

RFC 1034 - Domain Names: Concepts and Facilities
RFC 1035 - Domain Names: Implementation and Specification
RFC 3492 - Punycode: A Bootstring encoding of Unicode for IDNA
RFC 5890 - IDNA: Definitions and Document Framework
RFC 5891 - IDNA: Protocol

RFC specifications are available in the spec/ directory for reference.

License#

ISC

Clone this repository

ocaml-publicsuffix - Public Suffix List for OCaml#