IPv6 address expand & compress

Client

One IPv6 address in — get a lowercase full 8- hextet form and an RFC 5952 compressed form (longest :: for runs of zero hextets, and ::ffff: dotted for IPv4-embedded). All client-side. See also CIDR calculator for /prefix and range.

Address only — not CIDR. For network/broadcast and prefix size, use the CIDR calculator (IPv4/IPv6).

IPv6

?

A zone index like %eth0 is accepted for parsing but not shown in the normalized output.

Expanded (8 groups)

2001:0db8:0000:0000:0000:0000:0000:0001

Compressed (RFC 5952)

2001:db8::1

Common use cases

  • Normalize strings from logs, ping output, and configs before you compare or diff them.
  • Show ::ffff:IPv4 in dotted form when working with dual-stack and mapped addresses.
  • Teach CIDR: pair with the CIDR page when you need both prefix math and a readable literal.
  • Copy compressed output into APIs or docs that expect a canonical 5952 string.

Common mistakes to avoid

  • Pasting a CIDR (address/prefix) here

    This page handles one address. Use the CIDR calculator for prefix length, network, and range on IPv6.

  • Expecting validation of your routing design

    It only rewrites the text. Policy and best practices still come from your network design.

  • Relying on %zone in the output

    A zone id may be part of the input, but the expanded and compressed lines drop it to show the address only.

FAQ

Is this the same as the IPv6 CIDR tab?

No. The CIDR calculator resolves /prefix; this tool only normalizes a single address string to expanded and compressed forms.

Is data sent to a server?

No. Conversion runs in your tab.

Common search terms

Phrases people search for that match this tool. See the full long-tail keyword index.

  • ipv6 expand to full form online
  • compress ipv6 address rfc 5952
  • ipv6 mapped ipv4 ::ffff
  • normalize ipv6 address in browser

More tools

Related utilities you can open in another tab—mostly client-side.