IPv6 addresses are 128 bits long. A new notation has been devised for writing these addresses. They are written as eight groups of four hexadecimal digits with colons between the groups. Have a look at the given example: If you roll over the binary presentation, the hexadecimal digits for each group are shown.
Since the addresses are really long, some optimizations have been proposed:
Leading zeros within a group can be omitted
One or more groups of 16 zero bits can be replaced by a pair of colons
See by yourself how the example address can be optimized. Just press the Play-Button!