Version 6 of the [[Internet Protocol]] uses 16-byte (128-bit) addresses. 128 bits creates a space of $2^{128}$, a number not very much different to the number of molecules on the surface of the earth. It is a very large number. It will nonetheless probably not be very efficiently used. They're written for humans as eight groups of four [[hexadecimal]] numbers, for example: > 8000:0000:0000:0000:0123:4567:89AB:CDEF Note above that there are three groups comprised solely of zeroes: these can be completely removed and replaced with a double colon, resulting in > 8000::0123:4567:89AB:CDEF Additionally, leading zeroes can be safely removed: > 8000::123:4567:89AB:CDEF Which makes the whole thing much easier to read We can also express an [[IPv4 address]] wth this notation: > ::192.168.1.0