is-localhost-ip

Comprehensive and robust library to checks whether given host name or IPv4/IPv6 address belongs to the local machine

Main difference from other libraries here is comprehensiveness: we start from strict RegExp checks (for IP address first, and then for correctness to be a host name), then fallback to DNS resolver (so it works with something like john.dev remapped locally in hosts or with local resolver).

All this in just ~100 lines of code without external dependencies.

Installation

npm i is-localhost-ip
# or
yarn add is-localhost-ip

Example

const isLocalhost = require('is-localhost-ip');

(async () => {
  await isLocalhost('127.0.0.1'); // true
  await isLocalhost('::ffff:127.0.0.1'); // true
  await isLocalhost('192.168.0.12'); // true
  await isLocalhost('192.168.0.12', true); // true only if the local machine has an interface with that address
  await isLocalhost('184.55.123.2'); // false

  await isLocalhost('tino.local'); // true
  await isLocalhost('localhost'); // true
  await isLocalhost('microsoft.com'); // false
})();

Caveats

Doesn't work with internationalized (RFC 3492 or RFC 5891) domain names. If you need that please use wonderful Punycode.js to convert the string before passing to this library:

const isLocalhost = require('is-localhost-ip');
const punycode = require('punycode');

(async () => {
  await isLocalhost(punycode.toASCII('свобода.рф')); // false
  await isLocalhost(punycode.toASCII('私の.家')); // true
})();

License

is-localhost-ip is available under the MIT license.