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IPv6 Address Validator

Check an IPv6 address, then see its canonical short form, its full 32-digit form and what kind of address it is.

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What is IPv6 Address Validator?

IPv6 addresses are eight groups of up to four hex digits separated by colons, and one run of zero groups may be shortened to "::". The same address therefore has many spellings. RFC 5952 defines the recommended canonical text form: lowercase, no leading zeros, and the longest zero run (at least two groups) compressed.

This tool validates strictly per RFC 4291, including IPv4-mapped tails such as ::ffff:192.0.2.1, brackets and %zone identifiers. It outputs the compressed and expanded forms, the decimal integer and hexadecimal value, and classifies the address: loopback, unspecified, link-local, unique local (ULA), multicast with scope, documentation, 6to4, Teredo, IPv4-mapped or global unicast.

How does it work?

  1. Paste one IPv6 address per line, in any valid spelling.
  2. A single address shows compressed, expanded, type, IPv4-mapped form and numeric values; several addresses appear in a table.
  3. Copy the canonical form for logs, ACLs or comparisons.
  4. Invalid input is explained: double "::", group longer than four digits, wrong number of groups, and so on.

Common use cases

  • Normalizing IPv6 addresses before comparing or de-duplicating them in logs.
  • Expanding an address to 32 hex digits to build reverse DNS (ip6.arpa) names or documentation.
  • Identifying whether an address is link-local, ULA or globally routable.
  • Debugging a config where an address was truncated or has two "::".

Examples

Try this input in the tool above:

Input
2001:0db8:0000:0000:0000:ff00:0042:8329
Output
Compressed (RFC 5952): 2001:db8::ff00:42:8329
Expanded: 2001:0db8:0000:0000:0000:ff00:0042:8329
Type: Documentation (2001:db8::/32)
Decimal integer: 42540766411282592856904265327123268393
Hexadecimal: 0x20010DB8000000000000FF0000428329

Privacy

IPv6 Address Validator runs entirely in your browser. The text or files you provide are processed on your device and are not uploaded, logged or stored on our servers.

Limitations

The tool checks syntax and address type only; it cannot confirm that an address exists or is reachable. Zone identifiers are accepted but are not part of the address value.

Frequently asked questions

Why can "::" appear only once?

If it appeared twice, the number of zero groups each one stands for would be ambiguous. The rule keeps every address unambiguous.

What does RFC 5952 canonical form mean?

Lowercase hex, leading zeros removed, and the longest run of zero groups (two or more) replaced by "::"; the first run wins a tie. A single zero group is not compressed.

What is fe80::1%eth0?

A link-local address with a zone identifier naming the local interface. The zone is needed by the OS to pick the interface but is not part of the address.

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