IPv6 toolbox
Expand, compress, normalize, classify, and calculate IPv6 prefix ranges locally.
Inputs stay in your browser
Interactive tool
Enable JavaScript to use the interactive controls. The guide below is available without JavaScript.
The IPv6 toolbox combines address formatting and prefix range calculation. The formatting module applies RFC 5952 representation rules, while the prefix module uses 128-bit integer arithmetic to find start and end addresses.
When to use this tool
- Normalize an IPv6 address before using it in documentation or configuration.
- Check the first and last address in a /64, /128, or other IPv6 prefix.
How to use
- Enter an IPv6 address without a zone ID.
- Use the formatting module for expanded and RFC 5952 output.
- Use the prefix module for start address, end address, and exact address count.
Example
Documentation prefix
2001:db8::1 is recognized as documentation space and is not suitable for public lookup.
How it works
- The parser expands :: once, converts eight 16-bit groups to a 128-bit BigInt, and compresses the longest zero run according to RFC 5952.
Limits and notes
- Zone IDs such as %en0 are not supported.
- DNS, reverse DNS, and network lookup are not performed.
- IPv4-mapped IPv6 is parsed but no X-forwarded or proxy interpretation is attempted.
Frequently asked questions
Can one zero group be compressed?
No. RFC 5952 avoids compressing a single 0000 group.
Does this page query the network?
No. IPv6 formatting and prefix calculations run locally in the browser.
References
Related tools
Send tool feedback
The message includes page context only, never tool input or results.
Send tool feedback