WhatAllows you to do Joi.string().phoneNumber(). Uses https://github.com/ruimarinho/google-libphonenumber for validation. Which is a compiled version of the Google library https://github.com/googlei18n/libphonenumber.const myCustomJoi = Joi.extend(require('joi-phone-number')); myCustomJoi.string().phoneNumber().validate('+32494567324'); // The phone number can be transformed to a custom format // Note that this follows Joi's `convert` option myCustomJoi.string().phoneNumber({ defaultCountry: ...