Repository: github.com/mirasayon/better-psl
NPM package url: www.npmjs.com/package/better-psl
better-psl is a modern JavaScript domain name parser based on the
Public Suffix List.
The Public Suffix List is a cross-vendor initiative to provide an accurate list of domain name suffixes.
The Public Suffix List is an initiative of the Mozilla Project, but is maintained as a community resource. It is available for use in any software, but was originally created to meet the needs of browser manufacturers.
A "public suffix" is one under which Internet users can directly register names. Some examples of public suffixes are ".com", ".co.uk" and "pvt.k12.wy.us". The Public Suffix List is a list of all known public suffixes.
Source: publicsuffix.org
This module is currently only available for Node.js. See below for details.
This module is tested on Node.js v20 and v22
npm install better-pslThe package is ESM-only
import psl from "better-psl";or
import { get, isValid, parse, rules } from "better-psl";Parse domain based on Public Suffix List. Returns an Object with the following
properties:
tld: Top level domain (this is the public suffix).sld: Second level domain (the first private part of the domain name).domain: The domain name is thesld+tld.subdomain: Optional parts left of the domain.
Parse domain without subdomain:
import psl from "better-psl";
const { parsed } = psl.parse("google.com");
if (parsed) {
console.log(parsed);
// parsed: {
// input: "google.com",
// tld: "com",
// sld: "google",
// domain: "google.com",
// subdomain: null,
// listed: true,
// };
}Parse domain with subdomain:
import psl from "better-psl";
const { parsed, error } = psl.parse("www.google.com");
if (error) {
// return
}
if (parsed) {
console.log(parsed);
// parsed: {
// input: "www.google.com",
// tld: "com",
// sld: "google",
// domain: "google.com",
// subdomain: "www",
// listed: true,
// };
}Parse domain with nested subdomains:
import psl from "better-psl";
const { parsed, error } = psl.parse("a.b.c.d.foo.com");
if (error) {
// return;
}
console.log(parsed);
// parsed: {
// input: "a.b.c.d.foo.com",
// tld: "com",
// sld: "foo",
// domain: "foo.com",
// subdomain: "a.b.c.d",
// listed: true,
// };Get domain name, sld + tld. Returns null if not valid.
import psl from "better-psl";
// null input.
psl.get(null); // null
psl.get(undefined); // null
psl.get("some-thing-else"); // null
// Mixed case.
psl.get("COM"); // null
psl.get("example.COM"); // 'example.com'
psl.get("WwW.example.COM"); // 'example.com'
// Unlisted TLD.
psl.get("example"); // null
psl.get("example.example"); // 'example.example'
psl.get("b.example.example"); // 'example.example'
psl.get("a.b.example.example"); // 'example.example'
// TLD with only 1 rule.
psl.get("biz"); // null
psl.get("domain.biz"); // 'domain.biz'
psl.get("b.domain.biz"); // 'domain.biz'
psl.get("a.b.domain.biz"); // 'domain.biz'
// TLD with some 2-level rules.
psl.get("uk.com"); // null);
psl.get("example.uk.com"); // 'example.uk.com');
psl.get("b.example.uk.com"); // 'example.uk.com');
// More complex TLD.
psl.get("c.kobe.jp"); // null
psl.get("b.c.kobe.jp"); // 'b.c.kobe.jp'
psl.get("a.b.c.kobe.jp"); // 'b.c.kobe.jp'
psl.get("city.kobe.jp"); // 'city.kobe.jp'
psl.get("www.city.kobe.jp"); // 'city.kobe.jp'
// IDN labels.
psl.get("食狮.com.cn"); // '食狮.com.cn'
psl.get("食狮.公司.cn"); // '食狮.公司.cn'
psl.get("www.食狮.公司.cn"); // '食狮.公司.cn'
// Same as above, but punycoded.
psl.get("xn--85x722f.com.cn"); // 'xn--85x722f.com.cn'
psl.get("xn--85x722f.xn--55qx5d.cn"); // 'xn--85x722f.xn--55qx5d.cn'
psl.get("www.xn--85x722f.xn--55qx5d.cn"); // 'xn--85x722f.xn--55qx5d.cn'Check whether a domain has a valid Public Suffix. Returns a Boolean indicating
whether the domain has a valid Public Suffix.
import psl from "better-psl";
psl.isValid("google.com"); // true
psl.isValid("www.google.com"); // true
psl.isValid("x.yz"); // false# Update rules from publicsuffix.org
npm run update-rules
# Build and create dist files
npm run buildFeel free to fork if you see possible improvements!
- Mozilla Foundation's Public Suffix List
- Inspired by weppos/publicsuffix-ruby
The MIT License (MIT)
Copyright (c) 2025 "Mirasayon" [email protected]
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.