Kernaali ToolsHow it works
Expansion pads all eight groups to four hexadecimal digits. Compression removes leading zeros, lowercases letters and replaces the longest run of at least two zero groups with ::. Equal-length ties use the leftmost run.
Worked example
2001:0db8:0000:0000:0042:0000:0000:0001 compresses to 2001:db8::42:0:0:1. The first two-zero run wins the tie.
Inputs, edge cases & common mistakes
A single zero group is not compressed. Only one :: is allowed. Embedded dotted IPv4 is accepted and normalized to hexadecimal groups; mapped-address dotted display is not preserved. Prefix lengths and interface zone IDs are not part of this address-only input.
Technical references
Reviewed 9 September 2026. Found an issue? Send a correction with a reproducible example.