IPv6 Address Compressor/Expander
Paste any valid IPv6 address in any form and get both its fully compressed and fully expanded equivalents.
About this tool
Accepts an IPv6 address in any valid textual form — fully written out, already using the :: shorthand, or with leading zeros already stripped from individual groups — and shows both a canonical compressed form and a fully expanded form, updating live as you type.
The compressed output follows RFC 5952's rules precisely: leading zeros are stripped from every group, and the single longest run of two-or-more consecutive all-zero groups is replaced with ::. If there's a tie for longest run, the first one is compressed. A lone zero group on its own is deliberately left as 0 rather than compressed — RFC 5952 recommends against using :: for a run of just one zero group, since it saves no characters and can make addresses harder to compare at a glance.
This tool does not handle the embedded-IPv4 dual notation (addresses like ::ffff:192.168.1.1) — that's a distinct textual format and is out of scope here.