Pick a tool for IPv4 or IPv6 work. Every calculation runs in your browser. Nothing is uploaded. WHOIS, geolocation, and reverse DNS need the network and live under Special Ranges as external links.
IP address tools
Lookup
IP Inspector
Parse IPv4/IPv6 or CIDR: network, hosts, mask, class, binary.
Open tool →Contain
Subnet Membership
Check if an IP sits in a CIDR, same-subnet tests, and distance.
Open tool →Plan
Subnet Planner
Expand hosts, split prefixes, summarize, range→CIDR, random IP.
Open tool →Convert
IP Converter
Mapped IPv6, 6to4, Teredo, netmask↔prefix, MAC→link-local.
Open tool →Batch
IP Batch Validator
Validate lists of addresses and optionally check a CIDR.
Open tool →Reference
IP Special Ranges
Offline reserved blocks plus external WHOIS, geo, DNS, BGP links.
Open tool →