IPv6 address expander and compressor
Normalises how an IPv6 address is written before you put it in a firewall rule, a DNS record or compare it in a sheet.
Loading the tool…
Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter ipv6 address.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Expand: replace :: with the missing zero groups and pad each group to 4 digits. Compress (RFC 5952): drop leading zeros, replace the longest run of 2+ zero groups with :: (the first on a tie), lowercase.
Example
Inputs: IPv6 address = 2001:0DB8:0000:0000:0001:0000:0000:0001. Result: Compressed (RFC 5952): 2001:db8::1:0:0:1.
2001:0DB8:0000:0000:0001:0000:0000:0001
2001:db8::1:0:0:1
Limits and caveats
- Zone ids such as %eth0 and prefix lengths such as /64 are not accepted; remove them first.
- IPv4-mapped addresses are shown in mixed notation, as RFC 5952 recommends.
Questions about this tool
Can :: appear more than once?
No. That would make the number of zero groups ambiguous, so the tool rejects it.
Why is a single zero group not shortened?
RFC 5952 says :: must not stand for just one zero group, so it stays as 0.
What is the ip6.arpa name for?
You need it to create a PTR record so the address resolves back to a hostname.