IP protocol tools

IPv6 Compress & Expand

Turn any valid IPv6 address into its shortest canonical form or full eight-group notation—with clear validation and optional CIDR support.

Instant conversion Runs in your browser RFC-style normalization
Same 128-bit address2001:0db8:0000:0000:0000:0000:0000:00012001:db8::1Leading zeros removed · longest zero run compressed
01

Enter an IPv6 address

Compressed, expanded, or IPv4-mapped notation is accepted. Add an optional prefix such as /64.

Private, client-side tool
Try an example:

Hexadecimal letters are case-insensitive. Prefix lengths must be between /0 and /128.

Your converted addresses will appear here

Enter an IPv6 address above to compare canonical compressed and fully expanded notation.

What does this IPv6 converter do?

The tool checks whether an IPv6 address is valid and displays the same 128-bit value in two forms: canonical compressed notation and fully expanded notation. It preserves an optional CIDR prefix length, uses lowercase hexadecimal output, and performs the conversion locally in your browser.

How to compress or expand an IPv6 address

1. Enter the address

Paste compact notation such as 2001:db8::1 or all eight groups such as 2001:0db8:0000:0000:0000:0000:0000:0001.

2. Include CIDR if needed

Add a prefix from /0 through /128. The prefix is preserved, but the tool does not calculate the subnet range.

3. Compare and copy

Check both outputs before copying one into documentation, DNS, a firewall rule, or a device configuration.

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?

One IPv6 value can be written in several valid ways. Normalizing it makes log searches, access-list reviews, documentation, DNS checks, and configuration comparisons more reliable. Use the compressed form for normal display and the expanded form when you need to compare every 16-bit group.

How to use the output safely

Confirm that any CIDR prefix still matches your intended network before applying the address to a router, firewall, cloud rule, or DNS record. Text conversion does not verify reachability, ownership, interface scope, gateway configuration, or whether the address belongs to the intended subnet.

Limitations and privacy

This tool validates and reformats IPv6 notation only. It does not send the address to a lookup API, test whether it is online, or perform ping, traceroute, DNS, ASN, or port checks. 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, representing a total of 128 bits.

Can I include a /64 prefix?

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

Why can :: appear only once?

A second double colon would make it impossible to know how many zero groups belong in each omitted section.

Does the converter calculate the network address?

No. It preserves the prefix length and changes notation only; it does not mask host bits or calculate an address range.

Can it handle an IPv4-embedded form?

Yes, valid forms such as ::ffff:192.0.2.128 can be parsed and normalized.

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