An IPv6 address contains 128 bits, four times the length of an IPv4 address in bits.
IPv6 was designed to solve the Internet’s address-exhaustion problem. Its 128-bit address space provides 2^128 possible addresses, an enormously larger pool than IPv4’s 2^32 addresses. IPv6 addresses are normally written as eight groups of four hexadecimal digits, separated by colons, such as 2001:db8::1.
The notation can be shortened by removing leading zeroes and replacing one consecutive run of all-zero groups with a double colon. This compression is only a display rule; the address still represents 128 bits. IPv6 also supports address types such as unicast, multicast, and anycast.
A frequent mistake is confusing address length with hexadecimal characters. A fully expanded IPv6 address has 32 hexadecimal digits, and each hexadecimal digit represents four bits, producing 128 bits in total. IPv6 adoption continues alongside IPv4, with many networks using both protocols.