Writing IPv6 addresses (explained)

An IPv6 address is usually written as eight blocks of four hexadecimal digits, with each block separated by a colon.

Example: 2001:0B80:0000:0000:0000:0F80:3FA8:18AB

You may shorten addresses by eliminating leading zeros in a block. Also, note that some of the four-digit blocks may consist of zeros only. If any number of such 0000 blocks are consecutive, you may shorten addresses by replacing the 0000 blocks with two colons as long as there is only one such double colon in the address.

Example:
2001:0B80:0000:0000:0000:0F80:3FA8:18AB can be shortened to

2001:B80:0000:0000:0000:F80:3FA8:18AB if removing the leading zeros, or to

2001:0B80::0F80:3FA8:18AB if removing the 0000 blocks, or even to

2001:B80::F80:3FA8:18AB if removing the leading zeros as well as the 0000 blocks.