Why this tool is useful
Use normalization to compare equivalent IPv6 spellings, prepare stable test fixtures and remove ambiguity from configuration reviews without resolving or contacting any address.
Developer & Data · runs locally
IPv6 Address Normalizer
Validate IPv6 text and show both fully expanded notation and RFC 5952-style lowercase compression, including IPv4-mapped addresses.
Ready. Your working data stays in this browser.
How it works
The parser expands one optional double-colon, validates all eight 16-bit groups and any final embedded IPv4 address, then compresses the first longest zero run and removes leading zeros.
Practical example
2001:0DB8:0:0:0:0:2:1 becomes canonical 2001:db8::2:1 while the expanded form retains eight four-digit hexadecimal groups.
Validation
The calculation is deterministic and explains validation errors instead of silently changing invalid input.
Privacy boundary
Input and output remain in this tab. Copy and download happen through browser APIs without a server upload.
Result passport
Every run reports its tool mode, timestamp and input/output size so transformed data can be audited.