# is-cidr [](https://www.npmjs.org/package/is-cidr) [](https://www.npmjs.org/package/is-cidr) [](https://travis-ci.org/silverwind/is-cidr) > Check if a string is an IP address in CIDR notation ## Install ``` npm i is-cidr ``` ## Usage ```js const isCidr = require('is-cidr'); isCidr('192.168.0.1/24'); //=> 4 isCidr('1:2:3:4:5:6:7:8/64'); //=> 6 isCidr('10.0.0.0'); //=> 0 isCidr.v6('10.0.0.0/24'); //=> false ``` ## API ### isCidr(input) Check if `input` is a IPv4 or IPv6 CIDR address. Returns either `4`, `6` (indicating the IP version) or `0` if the string is not a CIDR. ### isCidr.v4(input) Check if `input` is a IPv4 CIDR address. Returns a boolean. ### isCidr.v6(input) Check if `input` is a IPv6 CIDR address. Returns a boolean. ## Related - [cidr-regex](https://github.com/silverwind/cidr-regex) - Regular expression for matching IP addresses in CIDR notation - [is-ip](https://github.com/sindresorhus/is-ip) - Check if a string is an IP address - [ip-regex](https://github.com/sindresorhus/ip-regex) - Regular expression for matching IP addresses ## License © [silverwind](https://github.com/silverwind), distributed under BSD licence Based on previous work by [Felipe Apostol](https://github.com/flipjs)