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tld.js Build Status

tld.js is JavaScript API to work against complex domain names, subdomains and well-known TLDs.

It answers with accuracy to questions like what is domain?, what is subdomain? and is TLD a well-known one?.

tld.js runs fast, is fully tested and works both in Node.js and in the browser. Because it relies on Mozilla's public suffix list, now is a good time to say thank you Mozilla!


# With bundled Top Level Domains list 
npm install --save tldjs
# You can get an up-to-date Top Level Domains list during the install 
npm install --save tldjs --tldjs-update-rules

The latter is useful if this package has not been published for a while on npm.

Using It


const { parse } = require('tldjs');
{ hostname: '',
  isValid: true,
  tldExists: true,
  publicSuffix: '',
  domain: '',
  subdomain: 'mail' }


A browser version is made available thanks to browserify CDN.

<script src="">
// { hostname: '',
//   isValid: true,
//   tldExists: true,
//   publicSuffix: '',
//   domain: '',
//   subdomain: 'mail' }

You can build your own browser bundle with browserify:

npm install --save browserify
browserify -s tld -r tldjs -o tld.js

An UMD module will be created as of tld.js.


tldjs can be use either as a whole, or using destructuring.

// ES2015 modules syntax
import tldjs from 'tldjs';
import { parse } from 'tldjs';
// Node/CommonJS modules syntax
const tldjs = require('tldjs');
const { parse } = require('tldjs');


This methods returns handy properties about a URL or a hostname.

const tldjs = require('tldjs');
// { hostname: '',
//   isValid: true,
//   tldExists: true,
//   publicSuffix: 'com',
//   domain: '',
//   subdomain: 'www' }
// { hostname: 'domain.unknown',
//   isValid: true,
//   tldExists: false,
//   publicSuffix: 'unknown',
//   domain: 'domain.unknown',
//   subdomain: '' }
// { hostname: '',
//   isValid: true,
//   tldExists: true,
//   publicSuffix: 'com',
//   domain: '',
//   subdomain: 'community' }
Property Name Type
hostname String
isValid Boolean Is the hostname valid according to the RFC?
tldExists Boolean Is the TLD well-known or not?
publicSuffix String
domain String
subdomain String

Single purpose methods

These methods are shorthands if you want to retrieve only a single value


Checks if the TLD is well-known for a given hostname — parseable with require('url').parse.

const { tldExists } = tldjs;
tldExists('');      // returns `true`
tldExists('google.local');    // returns `false` (not an explicit registered TLD)
tldExists('com');             // returns `true`
tldExists('uk');              // returns `true`
tldExists('');           // returns `true` (because `uk` is a valid TLD)
tldExists(''); // returns `true` (still because `uk` is a valid TLD)
tldExists('');    // returns `true` (still because `uk` is a valid TLD)
tldExists(''); // returns `true`


Returns the fully qualified domain from a given string — parseable with require('url').parse.

const { getDomain } = tldjs;
getDomain('');        // returns ``
getDomain('');     // returns ``
getDomain('');  // returns ``
getDomain('');  // returns ``
getDomain('');              // returns ``
getDomain('');           // returns ``
getDomain(''); // returns ``


Returns the complete subdomain for a given string — parseable with require('url').parse.

const { getSubdomain } = tldjs;
getSubdomain('');             // returns ``
getSubdomain('');          // returns `fr`
getSubdomain('');           // returns ``
getSubdomain('');       // returns `foo`
getSubdomain('');  // returns ``
getSubdomain('');                   // returns ``
getSubdomain('');                // returns `fr`
getSubdomain(''); // returns `secure`


Returns the public suffix for a given string — parseable with require('url').parse.

const { getPublicSuffix } = tldjs;
getPublicSuffix('');       // returns `com`
getPublicSuffix('');    // returns `com`
getPublicSuffix('');     // returns ``
getPublicSuffix(''); // returns ``
getPublicSuffix('');   // returns `unknown`


Checks the validity of a given string — parseable with require('url').parse. It does not check if the TLD is well-known.

const { isValid } = tldjs;
isValid('');      // returns `true`
isValid('');     // returns `false`
isValid('my.fake.domain');  // returns `true`
isValid('localhost');       // returns `false`
isValid(''); // returns `true`


Retrieving subdomain of localhost and custom hostnames

tld.js methods getDomain and getSubdomain are designed to work only with known and valid TLDs. This way, you can trust what a domain is.

localhost is a valid hostname but not a TLD. Although you can instanciate your own flavour of tld.js with additional valid hosts:

const tldjs = require('tldjs');
tldjs.getDomain('localhost');           // returns null
tldjs.getSubdomain('vhost.localhost');  // returns null
const myTldjs = tldjs.fromUserSettings({
  validHosts: ['localhost']
myTldjs.getDomain('localhost');           // returns 'localhost'
myTldjs.getSubdomain('vhost.localhost');  // returns 'vhost'

Updating the TLDs List

Many libraries offer a list of TLDs. But, are they up-to-date? And how to update them?

tld.js bundles a list of known TLDs but this list can become outdated. This is especially true if the package have not been updated on npm for a while.

Hopefully for you, even if I'm flying over the world, if I've lost my Internet connection or even if you do manage your own list, you can update it by yourself, painlessly.

How? By passing the --tldjs-update-rules to your npm install command:

# anytime you reinstall your project 
npm install --tldjs-update-rules
# or if you add the dependency to your project 
npm install --save tldjs --tldjs-update-rules

Open an issue to request an update of the bundled TLDs.


Provide a pull request (with tested code) to include your work in this main project. Issues may be awaiting for help so feel free to give a hand, with code or ideas.


While interpreting the results, keep in mind that each "op" reported by the benchmark is processing 24 domains
tldjs#isValid x 230,353 ops/sec ±10.99% (44 runs sampled)
tldjs#extractHostname x 42,333 ops/sec ±2.82% (85 runs sampled)
tldjs#tldExists x 15,083 ops/sec ±8.76% (54 runs sampled)
tldjs#getPublicSuffix x 14,334 ops/sec ±8.00% (80 runs sampled)
tldjs#getDomain x 15,092 ops/sec ±1.92% (84 runs sampled)
tldjs#getSubdomain x 13,202 ops/sec ±3.66% (72 runs sampled)
tldjs#parse x 8,561 ops/sec ±11.78% (55 runs sampled)

You can measure the performance of tld.js on your hardware by running the following command:

npx tldjs -c './bin/benchmark.js'


MIT License.