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IPv6 Expander & Validator

Expand, compress and validate IPv6 addresses, including embedded IPv4, with hex and binary forms and the network and address count of a CIDR.

IPv6 Expander & Validator

Valid IPv6 address, prefix /64

Expanded (full)
2001:0db8:85a3:0000:0000:8a2e:0370:7334
Compressed (RFC 5952)
2001:db8:85a3::8a2e:370:7334
Hex (128-bit)
0x20010db885a3000000008a2e03707334
Binary (128-bit)
00100000000000010000110110111000100001011010001100000000000000000000000000000000100010100010111000000011011100000111001100110100
CIDR / Prefix details
Prefix length
/64
Network address
2001:db8:85a3::
Addresses in range
2^64
Network (expanded): 2001:0db8:85a3:0000:0000:0000:0000:0000
Exact count: 18,446,744,073,709,551,616

Updated . Provided as is. Check the output before you rely on it in production.

How to use IPv6 Expander & Validator

  1. 1

    Enter an address or CIDR

    Type or paste an IPv6 address like 2001:db8::1, optionally with a prefix such as /64, or load the sample to start.

  2. 2

    Read the expanded and compressed forms

    Compare the full eight-group form with the RFC 5952 canonical form, plus the 128-bit hex and binary representations.

  3. 3

    Check the prefix details

    When you include a CIDR prefix, review the network address and the total number of addresses in the block.

  4. 4

    Copy what you need

    Use the copy button on any field to grab the expanded, compressed, hex, or binary value.

Questions and answers

What does the IPv6 Expander do?
An IPv6 address is 128 bits written as eight hex groups, often shortened by dropping leading zeros and replacing one run of zero groups with ::. This tool validates an address or CIDR and shows the full form, the RFC 5952 compressed form, hex and binary values and, for a prefix, the network and address count.
How do I expand a shortened IPv6 address?
Paste the address using its :: shorthand and the tool fills in the omitted zero groups, returning all eight 16-bit groups in full.
What does the address count mean for a CIDR?
For a /n prefix it reports 2^(128-n), the number of addresses the block contains, shown both as a power of two and as an exact integer.
Does it handle embedded IPv4 addresses?
Yes. Mixed notation such as ::ffff:192.0.2.1 is parsed correctly, converting the dotted-quad tail into its two hexadecimal groups.
Is my address sent to a server?
No. All parsing and the BigInt math run locally in your browser, so the address you enter is never transmitted.
For AI agents: how to call this tool

Machine-readable contract, endpoints and examples. Humans can ignore this section.

Best Path For Builders

Browser workflow

Runs instantly in the browser with private local processing and copy/export-ready output.

Browser Workflow

This tool is optimized for instant in-browser execution with local data handling. Run it here and copy/export the output directly.

/ipv6-expander/

For automation planning, fetch the canonical contract at /api/tool/ipv6-expander.json.