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What Is IPv6? Address Format and Scope Explained
Published Jun 1, 2026
What Is IPv6?
IPv6 (Internet Protocol version 6) is the successor to IPv4, using 128-bit addresses instead of 32-bit. That yields roughly 340 undecillion addresses — enough for every device on Earth many times over.
An IPv6 address has eight hextets (16-bit groups) written in hexadecimal, separated by colons:
2001:0db8:85a3:0000:0000:8a2e:0370:7334
2001:db8::1 ← compressed form
fe80::1 ← link-local
::1 ← loopback
Use the IPv6 Address Tools to expand, compress, validate, and inspect scope.
Why IPv6 exists
IPv4's ~4.3 billion addresses are exhausted. NAT extends IPv4 but adds complexity. IPv6 restores end-to-end addressing and simplifies routing with hierarchical allocation.
Compression rules
- Leading zeros in each hextet may be omitted:
0db8→db8 - One contiguous run of all-zero hextets may be replaced with
:: - Only one
::per address
Common scopes
| Address | Scope | Use |
|---|---|---|
::1 | Loopback | Local host (like 127.0.0.1) |
fe80::/10 | Link-local | Same LAN segment only |
fc00::/7 | Unique local (ULA) | Private networks (like RFC 1918) |
2000::/3 | Global unicast | Public routable internet |
ff00::/8 | Multicast | One-to-many delivery |
IPv6 vs IPv4 at a glance
| IPv4 | IPv6 | |
|---|---|---|
| Length | 32 bits | 128 bits |
| Notation | Dotted decimal | Hex hextets |
| Broadcast | Yes | No (uses multicast) |
| NAT | Common | Designed to reduce need |
| Config | Manual / DHCP | SLAAC + DHCPv6 |