IP-API.com Geolocation API

IP-API.com is a website that allows users to lookup the location of an IP address. The site provides free usage of its geolocation API and supports IPv4/IPv6 queries. The API allows users to supply an IP address or domain to lookup, or none to use their current IP address. Data returned includes country, region/state, city, zip code, latitude, longitude and more. The API uses RESTful calls and responses can be formatted in XML, JSON, CSV, Newline Separated and PHP.