Domain Parser

A full-Swift simple library which allows the parsing of hostnames, using the Public Suffix List.

This Library allows finding the domain name and the public suffix / top-level-domain for a given URL.

What is the Public Suffix List ?

The PSL lists all the known public suffixes (like: com, co.uk, nt.edu.au, ...). Without this information we are not able to determine which part of a URL is the domain, since a suffix can have more than one Label. A suffix rule may also contain wildcards or exceptions to wildcards. If you want to understand the full format of PSL matching rules, you can read their specification here.

The PSL is continuously updated.

The list includes ICANN suffixes (official top level domains) but also private suffixes (like us-east-1.amazonaws.com).

Examples:

URL host	Domain	Public suffix	Matched PSL rule	Explanation
auth.impala.dashlane.com	dashlane.com	com	com	Simple rule
sub.domain.co.uk	domain.co.uk	co.uk	co.uk	Simple rule
sub.domain.gov.ck	domain.gov.ck	gov.ck	*.ck	Wildcard rule
sub.domain.any.ck	domain.any.ck	any.ck	*.ck	Wildcard rule
sub.sub.domain.any.ck	domain.any.ck	any.ck	*.ck	Wildcard rule
www.ck	www.ck	ck	!www.ck	Exception rule
sub.www.ck	www.ck	ck	!www.ck	Exception rule
sub.sub.www.ck	www.ck	ck	!www.ck	Exception rule

Usage

Initialization:

import DomainParser
...
let domainParser = try DomainParser()

You should use the same instance when you parse multiple URL hosts.

let domain: String? = domainParser.parse(host: "awesome.dashlane.com")?.domain
print(domain ?? "N/A") // dashlane.com

let suffix1: String? = domainParser.parse(host: "awesome.dashlane.com")?.publicSuffix
print(suffix1 ?? "N/A") // com

let suffix2: String? = domainParser.parse(host: "awesome.dashlane.co.uk")?.publicSuffix
print(suffix2 ?? "N/A") // co.uk

Update the local Public Suffix List

The local PSL used by the library is located at DomainParser/DomainParser/Resources/public_suffix_list.dat.

To update it, run this Terminal command in the script folder:

swift UpdatePSL.swift