Calculates network, broadcast, netmask and wildcard, first and last host, usable and total addresses, class and address type (private, CGNAT, loopback, link-local, documentation, multicast, …), binary/integer/hex forms and the reverse DNS name for IPv4; and network range, expanded/compressed forms (RFC 5952), address count as a power of two, type (global unicast, ULA, link-local, IPv4-mapped, …) and ip6.arpa name for IPv6. Enter a new prefix to split each network into subnets (up to 1,024). /31 networks follow RFC 3021. Everything runs locally.