IP info: what kind of address is this?

Paste a single IPv4 or IPv6 address — not a CIDR block — and this tool reports its version, its IANA special-use classification if it falls inside a reserved range, and the reverse-DNS name form (.in-addr.arpa or .ip6.arpa) that address would have. Every result is computed in your browser from the address’s own bits: no DNS query, no geolocation database, and no claim about who owns or operates the address.

What it classifies

• Version — IPv4 or IPv6, parsed from the text you paste.
• IANA special-use category — whether the address falls inside a range the IPv4 or IPv6 Special-Purpose Address Registry reserves: private use (RFC 1918), loopback, link-local, Shared Address Space / CGNAT (RFC 6598), documentation, benchmarking, multicast, reserved — or, for IPv6, unique local address / ULA (RFC 4193), the NAT64 well-known prefix and the discard-only block. An address matching none of these is reported as global unicast — ordinarily routable on the public internet, though this tool has no way to confirm anyone actually announces a route for it.
• Legacy classful designation (IPv4 only) — the historical Class A/B/C/D/E a pre-CIDR router would have assigned by the address’s leading bits. CIDR superseded this decades ago for routing, but the class still determines whether an address block sits inside the multicast (D) or reserved (E) range.
• Reverse-DNS name form — the exact in-addr.arpa (IPv4) or ip6.arpa (IPv6) name a PTR lookup for that address would use, built purely from the address’s own digits/nibbles in reverse order; no PTR lookup is performed.

Reading the result

A “private” or other special-use result means the address is not expected to appear as a public-facing endpoint on the open internet — seeing one of these where a public address is expected usually points at a NAT, proxy, or misconfigured network boundary, not a problem with the address itself. A “global unicast” result only means the address sits outside every reserved range this tool checks; it is not proof the address is currently assigned to anyone, reachable, or safe. For your own connection’s actual public IP, ASN and approximate location, see what is my IP instead — that tool reads live request metadata rather than classifying arbitrary text you paste.

Limits

• No DNS, WHOIS, geolocation or ASN lookups are performed, ever — this is pure arithmetic over the address’s bits, so it cannot say who owns an address, where it is, or whether it is currently in use or routed.
• It covers the special-purpose ranges most lookups actually need (listed above), not every narrow carve-out in either IANA registry — rare allocations like IPv6’s ORCHIDv2 or AMT relay prefixes are not called out individually.
• A single address only — for a CIDR block’s network/broadcast/host-range math, see the subnet calculator instead.

See CGNAT and RFC 1918 private address for more on two of the categories this tool reports, and link-local address for what that range is for in both IPv4 and IPv6. For a device’s hardware (MAC) address instead of its IP, see MAC vendor lookup.