IPv6 expander & compressor
Expand a shortened IPv6 address to its full form, compress a full address to its shortest valid form, and validate the syntax — all live.
How IPv6 shorthand works
A full IPv6 address has eight groups of four hex digits, e.g. 2001:0db8:0000:0000:0000:8a2e:0370:7334. Two rules shorten it:
- Drop leading zeros in each group:
0db8→db8,0000→0. - Collapse one run of all-zero groups to
::— but only once per address, otherwise it would be ambiguous.
Applying both gives 2001:db8::8a2e:370:7334. This tool reverses the process to recover the canonical full form, which you often need for ACLs, reverse DNS and database storage.
Address types at a glance
::1— loopback (like 127.0.0.1).fe80::/10— link-local, valid only on the local segment.fc00::/7— unique local (the IPv6 equivalent of private addresses).2000::/3— global unicast, routable on the public internet.ff00::/8— multicast.
Frequently Asked Questions
Can :: appear twice in an IPv6 address?
No. The double colon may be used only once, because it represents “as many zero groups as needed” — using it twice would make the length ambiguous. This tool rejects such addresses as invalid.
Why expand an address that's already valid compressed?
Many systems — firewall rules, reverse-DNS (ip6.arpa) records, some databases and logs — expect or store the full, fixed-width form. Expanding makes addresses line up and compare reliably.
Is IPv6 more private than IPv4?
It can cut both ways. Privacy Extensions randomise the host portion to resist tracking, but a static or EUI-64 address can be very identifying. Read more in IPv4 vs IPv6 privacy.