IPv6 addresses can be represented as either a compressed short IPv6 address or a fully expanded uncompressed address. The fully expanded form does not allow for any errors that have been introduced due to compression rules which may have been overlooked or improperly implemented when shortening.
A fully expanded IPv6 address takes on the following format:
Expanding a compressed IPv6 address to its uncompressed form is an easy process and can be done with many online tools. By using the IPv6 address expander tool on this page, you can quickly and easily convert a compressed address into a fully uncompressed expanded one. Simply enter the IPv6 address and press the expand button.
Due to the fact that IPv6 addresses can be compressed to a shorter format, it may be useful to expand them into their full form for comparison or de-duplication. Alternatively compressing or recompressing improperly compressed addresses may be able to serve this same purpose.
Often times the compression rules are not followed correctly, while these addresses are still technically valid, they make comparing shortened addresses difficult to do.
When generating reverse DNS records, IPv6 addresses must use the fully expanded format.
Below are a few examples of addresses which when expanded to their full format all represent the same address. Take note of the differing leading zeros, different capitalisation of letters, and the inconsistent location of the ::.
2001:0db8:0000:0000:0001:0000:0000:0001 can be represented as:
There are several rules that need to be followed in order to expand an address. It is important to know that each address is represented by eight groups of four hexadecimal digits. The groups are separated by colons (:).
A properly expanded address takes the following format:
Any group with less than hexadecimal 4 digits should be padded with prefixed 0's. eg
Any groups compressed together with
:: should be expanded to
0000 until there are 8 groups in the address in total.
Any alpha digits in each group should be converted to lower case. eg
Any valid (or mostly valid) IPv6 address can be expanded, including addresses which were improperly or inconsistently compressed.
Some examples: ::1, 2002:7f00:001::, 2001:db8::2:1