IP protocol tools

IPv6 Compress & Expand Tool

Validate an IPv6 address and view its canonical compressed and full eight-group forms. Add an optional CIDR prefix such as /64.

Convert an IPv6 address

Enter a compressed or expanded IPv6 address. You can optionally include a prefix such as /64.

Examples: 2001:db8::1, ::1, 2001:db8::/64, or ::ffff:192.0.2.128.

How to use this tool

1. Enter an address

Paste an IPv6 address in either compact or full notation.

2. Add a prefix if needed

Include a CIDR suffix from /0 through /128.

3. Review and copy

Convert, compare both forms, then use the copy buttons when needed.

What is IPv6 compression?

IPv6 uses eight 16-bit hexadecimal groups. The text can be shortened by removing leading zeros from each group and compressing one consecutive run of zero groups. For example, 2001:0db8:0000:0000:0000:ff00:0042:8329 becomes 2001:db8::ff00:42:8329.

How does :: work?

A double colon replaces one or more consecutive all-zero groups. It can appear only once because two omitted runs would make the missing group counts ambiguous. Canonical formatting compresses the longest zero run; when runs are tied, it uses the leftmost one. A single zero group is written as 0, not ::.

What is expanded IPv6 notation?

Expanded notation always has eight colon-separated groups of four hexadecimal characters. For example, 2001:db8::1 expands to 2001:0db8:0000:0000:0000:0000:0000:0001.

Does IPv6 compression change the address?

No. Compressed and expanded representations identify the exact same 128-bit IPv6 address.

Practical examples

Documentation prefix

2001:0db8:0000:0000:0000:ff00:0042:8329

Compressed: 2001:db8::ff00:42:8329

Link-local example

fe80::1

Expanded: fe80:0000:0000:0000:0000:0000:0000:0001

Loopback

::1

Expanded: 0000:0000:0000:0000:0000:0000:0000:0001

Why normalize an IPv6 address?

A consistent representation makes address comparisons, documentation, troubleshooting, firewall configuration review, DNS/configuration verification and networking education easier. It does not mean every device or configuration system requires the same textual form.

Limitations and privacy

This tool validates and reformats IPv6 notation only. It does not test whether an address is online or verify ownership, and it performs no ping, traceroute, DNS, ASN or port check. Conversion occurs locally in your browser.

IPv6 compression FAQ

Are hexadecimal letters case-sensitive?

No. IPv6 hexadecimal digits are case-insensitive; canonical output here uses lowercase.

How many groups does IPv6 contain?

Every IPv6 address expands to eight four-digit hexadecimal groups.

Can I include a /64 prefix?

Yes. Prefix lengths from /0 through /128 are preserved in both outputs.

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