IPv6 Calculator
Validate, expand, compress, and calculate IPv6 prefixes without sending your address anywhere.
Examples: 2001:db8::1 or 2001:db8::/32
What this result means
IPv6 addresses are 128 bits long. Compressed notation is only a shorter way to write the same address, and /64 is common but not universal.
How this check works
IPv6 compression removes leading zeroes in each group and replaces one longest run of two or more all-zero groups with ::. Only one :: is allowed in a valid compressed address.
A prefix such as /64 fixes the first 64 bits; the remaining bits vary within that prefix. Unlike IPv4, IPv6 has no IPv4-style broadcast address, and the prefix address itself is the first address.
Reverse DNS uses nibble-reversed hexadecimal digits under ip6.arpa. This tool shows reverse DNS for the full address; it does not infer delegation for non-nibble-aligned prefixes.