About

IPv6 uses a 128-bit address space, yielding approximately 3.4 × 10³⁸ unique addresses. Generating test addresses by hand is error-prone. A misplaced colon or an incorrect group count invalidates the address entirely, breaking firewall rules, DNS records, or ACL entries before they reach production. This generator produces cryptographically random addresses using the browser's native CSPRNG (crypto.getRandomValues), applies canonical compression per RFC 5952, and respects user-defined prefix lengths so output falls within a target subnet.

The tool does not simulate randomness with Math.random. It draws from the operating system's entropy pool. Addresses are formatted with zero suppression and longest-run :: collapsing. Limitation: generated addresses are syntactically valid but not guaranteed routable. They are intended for testing, documentation, and configuration templating.

Formulas

An IPv6 address consists of 8 groups of 4 hexadecimal digits separated by colons, totaling 128 bits:

addr = g₁ : g₂ : g₃ : g₄ : g₅ : g₆ : g₇ : g₈

Where each g_i ∈ [0000, ffff] (16 bits). The total address space is 2¹²⁸.

When a prefix of length p is specified, the first p bits are fixed and the remaining 128 − p bits are randomized. The number of possible addresses within that subnet is:

N = 2^{(128 − p)}

RFC 5952 canonical compression: (1) remove leading zeros from each group, (2) find the longest consecutive run of all-zero groups, (3) replace that run with ::. If two runs tie in length, the leftmost wins. The :: substitution may appear at most once.

Where addr = full IPv6 address, g_i = the i-th 16-bit group, p = prefix length in bits, N = number of addresses in the subnet.

Reference Data

Prefix	Range	Scope / Purpose	RFC	Prefix Length	Example
::1	Loopback	Host-only, equivalent to 127.0.0.1	RFC 4291	/128	::1
::	Unspecified	Absence of address	RFC 4291	/128	::
fe80::	Link-Local Unicast	Single link, auto-configured	RFC 4291	/10	fe80::1
fc00::	Unique Local (L=0)	Private, not yet assigned	RFC 4193	/7	fc00::1
fd00::	Unique Local (L=1)	Private, locally assigned	RFC 4193	/8	fd12:3456::1
2001:db8::	Documentation	Examples and docs only	RFC 3849	/32	2001:db8::1
2001::	Teredo Tunneling	IPv6 over UDP/IPv4	RFC 4380	/32	2001::1
2002::	6to4 Relay	Automatic tunneling (deprecated)	RFC 3056	/16	2002:c0a8::1
2000::	Global Unicast	Public Internet routable	RFC 3587	/3	2607:f8b0:4004::1
ff00::	Multicast	One-to-many delivery	RFC 4291	/8	ff02::1
ff02::1	All Nodes (Link)	All link-local nodes	RFC 4291	/128	ff02::1
ff02::2	All Routers (Link)	All link-local routers	RFC 4291	/128	ff02::2
::ffff:0:0	IPv4-Mapped	IPv4 inside IPv6 socket	RFC 4291	/96	::ffff:192.168.1.1
64:ff9b::	NAT64 Well-Known	Stateful IPv4/IPv6 translation	RFC 6052	/96	64:ff9b::192.0.2.1
100::	Discard-Only	Black hole routing	RFC 6666	/64	100::1

Frequently Asked Questions

It uses the Web Crypto API (crypto.getRandomValues), which draws entropy from the operating system's cryptographic random number generator. This is the same source used for TLS key generation and is far superior to Math.random(), which is a PRNG and not suitable for security-sensitive address generation.

RFC 5952 defines the canonical text representation of IPv6. It removes leading zeros in each group (e.g., 0042 becomes 42) and replaces the longest consecutive sequence of all-zero groups with ::. For example, 2001:0db8:0000:0000:0000:0000:0000:0001 compresses to 2001:db8::1. Without compression, the full expanded form with all 32 hex digits plus 7 colons is shown.

Yes. Enter a prefix (e.g., 2001:db8::) and a prefix length (e.g., /32). The generator fixes the first p bits from your prefix and randomizes the remaining 128 − p bits. This means all output addresses will fall within that subnet. If the prefix you enter is shorter than the prefix length implies, trailing bits are zero-filled before masking.

Not necessarily. An address is syntactically valid but routability depends on whether the prefix is allocated by a Regional Internet Registry (RIR) and announced via BGP. Addresses in the 2001:db8::/32 range are explicitly reserved for documentation and must never appear in production routing tables. Link-local (fe80::/10) and unique-local (fd00::/8) addresses are non-routable by design.

The :: notation indicates one or more consecutive groups of all zeros have been collapsed. For instance, if groups 3 through 6 are all 0000, they collapse into ::. This is valid and expected. When parsing, expand :: back to the appropriate number of zero groups to restore the full 8-group address.

The tool allows up to 1000 addresses per batch. Generation uses typed arrays (Uint16Array) and completes in under 50 ms for 1000 addresses on modern hardware. For larger datasets, generate multiple batches and export each as a text file.

The prefix input defines the fixed network portion. The prefix length (/p) determines how many leading bits are preserved. If you enter fd00:: with /8, only the first 8 bits (fd) are locked. The remaining 120 bits are random. If your prefix contains more specific bits than the prefix length covers, those extra bits are overwritten by random data.