How to use this tool
- Enter a complete IPv6 address such as 2001:0db8:0000:0000:0000:0000:0000:0001.
- Select Format IPv6 to see its compressed and eight-group expanded forms.
- Copy the compressed address, or use CIDR calculator to inspect its network prefix.
Two ways to write the same value
An IPv6 address has eight groups of sixteen bits, commonly written in hexadecimal. Expanded notation pads every group to four digits. Compressed notation removes leading zeroes and replaces a run of all-zero groups with a double colon.
The double colon can appear only once in an address. This formatter uses lowercase hexadecimal and compresses the longest zero run, preferring the first when runs tie. It does not compress an isolated single zero group. These choices produce a consistent representation of the same numeric value.
What this input accepts
Enter an address without URL brackets, a port, a slash prefix or an interface zone such as %en0. A mapped form such as ::ffff:192.0.2.1 can be valid IPv6 notation; the formatter displays its equivalent hexadecimal groups and identifies its mapped classification.
Syntax validation does not tell you whether an address is globally routable. Documentation, loopback, unique-local and link-local addresses can all be syntactically valid. The address checker explains those categories in more detail.
Compare values, not just text
Uppercase letters, omitted leading zeroes and different valid compression can make equal addresses look different. Formatting them consistently helps when comparing copied results. An IPv6 address can also rotate for privacy, which is a separate issue from how it is written.
All formatting runs locally. The tool does not send the entered address to a lookup provider, test IPv6 connectivity or reveal another address from your device.