IP address Public, private, IPv4, IPv6, static or dynamic: everything about IP addresses. Hostname and DNS What a hostname is for, and how DNS and reverse DNS work. IP geolocation How an IP address can be used to estimate a location, and its limits. VPN and proxy What a VPN and a proxy are, and how they are detected. IP blacklist Why an IP gets blacklisted, and how to get it removed. WHOIS and IP registries Who owns an IP address, and how to find out via WHOIS.