Expand, compress and analyze IPv6 addresses including prefix and interface identifier breakdown.
IPv6 addresses are 128 bits written as eight groups of four hex digits. The '::' shorthand collapses consecutive all-zero groups. Expanding reverses this compression for analysis. The prefix length determines how many leading bits identify the network versus the interface.
Addresses in subnet
addresses = 2^(128 - prefix)
IPv6 was designed with a 64-bit network prefix and 64-bit interface identifier split in mind. SLAAC (Stateless Address Autoconfiguration) requires a /64 subnet to derive interface IDs from MAC addresses, making /64 the standard subnet size for end-user networks.
A single '::' replaces one or more consecutive groups of all zeros. It can only appear once in an address to avoid ambiguity about how many groups were compressed.