It uses a database of IP addresses, provided from geoip.nekudo.com, that are associated to cities and to other informations
What is IP Lookup?
IP Lookup is a Firefox add-on that utilizes the geoip.nekudo.com service to search for geolocation information associated with IP addresses. It provides details such as city, time zone, latitude, and longitude.
extreme-ip-lookup.com provides a public HTTP API for software developers to search the geolocation of IP addresses. This addon uses geoip.nekudo.com service: a database of IP addresses that are associated to cities along with other relevant information like time zone, latitude and longitude.
Release 1.6.0 - Using new IP API service to get json data. The function to export content result as html and pdf format has been removed for security reason
IP Lookup is risky to use as it requires a number of sensitive permissions that can potentially harm your browser and steal your data. Exercise caution when installing this add-on. Review carefully before installing. We recommend that you only install IP Lookup if you trust the publisher.
IP Lookup has earned a fairly good reputation and likely can be trusted.