IPv6 (Internet Protocol version 6, RFC 8200) is the successor to IPv4. An IPv6 address is a 128-bit number, written as eight groups of four hexadecimal digits separated by colons (RFC 4291):
2001:0db8:85a3:0000:0000:8a2e:0370:7334128 bits allow 2128 ≈ 3.4 × 1038 addresses.
How to shorten an IPv6 address
RFC 5952 sets the standard short form:
- Drop leading zeros in each group:
0db8→db8,0370→370,0000→0. - Replace the longest run of all-zero groups with
::— only once per address. - Use lowercase letters.
| Full form | Short form |
|---|---|
2001:0db8:85a3:0000:0000:8a2e:0370:7334 |
2001:db8:85a3::8a2e:370:7334 |
2001:0db8:0000:0000:0000:0000:0000:0001 |
2001:db8::1 |
0000:0000:0000:0000:0000:0000:0000:0001 |
::1 (loopback) |
Parts of an IPv6 address
- Network prefix — identifies the network. For typical unicast addresses the prefix is 64 bits (RFC 4291). Your ISP delegates a larger block to your connection; the RIPE community's best practice is a /48 or /56 per customer, and it says assigning a /64 or longer “does not conform to IPv6 standards” (RIPE-690).
- Interface ID (last 64 bits) — identifies the device's interface on that network (RFC 4291).
Common IPv6 address types
Main types below; the full list of reserved ranges is the IANA IPv6 Special-Purpose Address Registry.
| Prefix | Type | Meaning | Defined in |
|---|---|---|---|
2000::/3 |
Global unicast | Public, routable addresses — what this site shows you | IANA |
fe80::/10 |
Link-local | Valid only on the local link; every interface has one | RFC 4291 |
fc00::/7 |
Unique local | Private addresses (locally assigned ones start with fd) |
RFC 4193 |
::1 |
Loopback | “This computer”, like 127.0.0.1 | RFC 4291 |
ff00::/8 |
Multicast | Sent to a group of interfaces | RFC 4291 |
2001:db8::/32 |
Documentation | Reserved for examples | RFC 3849 |
Why does my IPv6 address keep changing?
Devices can generate temporary addresses with randomised interface IDs and use them for outgoing connections, so sites can't track a device by a fixed interface ID. RFC 8981 specifies this, with a default preferred lifetime of one day for each temporary address. Seeing a different IPv6 address here from day to day is expected.
IPv6 in URLs and commands
In a URL, an IPv6 address goes in square brackets (RFC 3986), especially when a port follows:
http://[2001:db8::1]:8080/To see your public IPv6 address from a terminal:
curl -6 https://forgotmyip.comIf that fails, your network has no IPv6 connectivity — that's when the home page shows IPv6 as “not detected”.
How common is IPv6?
Google publishes the share of its users who reach it over IPv6 (Google IPv6 statistics). That share passed 50% for the first time on 28 March 2026, at 50.10% (Internet Society Pulse). The figure varies day to day — check Google's page for the current number.