IP Address Inspector
Classify any IPv4 / IPv6 address: public, private, loopback, link-local, multicast.
Overview
The IP address inspector classifies any IPv4 or IPv6 address by its scope and special-use designation: public, private (RFC 1918), loopback, link-local, multicast, broadcast, reserved, documentation, or unique-local for IPv6. Paste an address and the tool returns the category, the RFC that defines it, and what kind of traffic should or should not be on it.
Network engineers triaging a firewall log, developers writing IP validation rules, and students learning the difference between private and public address space all need a quick IP classifier. Long-tail keywords covered: classify IPv4 address as public or private, detect loopback or link-local IP, and identify multicast vs broadcast addresses.
How it works
The IPv4 and IPv6 address spaces are carved into ranges with specific semantics. IPv4's RFC 1918 reserves 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 for private networks. 127.0.0.0/8 is loopback. 169.254.0.0/16 is link-local (APIPA). 224.0.0.0/4 is multicast. 100.64.0.0/10 is the carrier-grade NAT (CGNAT) range. Several blocks are reserved for documentation (192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24).
IPv6 has its own carve-out: ::1/128 is loopback, fe80::/10 is link-local, fc00::/7 is unique local (ULA, per RFC 4193), ff00::/8 is multicast, and 2001:db8::/32 is documentation. Everything else in 2000::/3 is global unicast — the bulk of public IPv6.
Examples
10.0.0.5→ private IPv4 (RFC 1918).127.0.0.1→ loopback IPv4.169.254.42.1→ link-local IPv4 (auto-configuration when DHCP fails).fd12:3456:789a::1→ IPv6 unique-local address (ULA).
FAQ
Is 100.64.0.0/10 private?
It is reserved for carrier-grade NAT (RFC 6598), so it is not routable on the public internet but it is not exactly "private" either — your ISP uses it between you and their public NAT pool. Some home routers also misuse it.
What is the difference between APIPA and link-local in general?
APIPA is the IPv4 auto-configuration mechanism that picks an address from 169.254.0.0/16 when no DHCP server is reachable. "Link-local" is the broader concept of an address that only works within a single network segment — IPv6 uses fe80::/10 for the same purpose, but it is always assigned, not just as a fallback.
Is 224.0.0.0/4 routable?
It is multicast. Routable across some boundaries within an administrative domain, but never across the open internet without explicit multicast peering.
Why are documentation ranges reserved?
So example traffic in books, RFCs, and tutorials cannot accidentally hit a real production network if someone copy-pastes a config.