IP Info

How to use IP Info

1. Type an IPv4 or IPv6 address.
2. Read its version, type, class and numeric representations.
3. Use the binary form when working out subnet boundaries by hand.
4. This analyses the address you enter; it does not detect your own IP or query a geolocation service.
5. Private addresses are meaningful only within their own network — the same one exists on millions of others.
6. The decimal integer form is what databases often store, since it sorts and ranges more efficiently than text.

Private ranges, and why they exist

Three IPv4 ranges are reserved for private networks and never routed on the public internet: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. Your home router almost certainly hands out addresses in the last of those. They exist because IPv4 has only 4.3 billion addresses, and the world ran out — private ranges plus network address translation let an entire household or office share one public address. That is also why you cannot reach a device on someone else’s 192.168.1.10: the address is meaningful only inside their network, and millions of networks use the same one.

Address classes are history, but the vocabulary survives

Classes A, B and C divided the address space by fixed boundaries, and were replaced by CIDR in 1993 because they wasted enormous blocks — an organisation needing 300 addresses had to take a class B of 65,536. CIDR allows any prefix length, written as /24 or /19, which is how allocation has worked for thirty years. The class terminology persists in conversation and in tools like this one, but nothing routes by it any more.

Special addresses worth recognising

127.0.0.1 is loopback — the machine talking to itself, and the whole 127.0.0.0/8 block is reserved for it. 0.0.0.0 means “any address” when a server binds to it and “unknown” as a source. 169.254.x.x is link-local, assigned automatically when DHCP fails, and seeing it means the machine never got an address from the router — a useful diagnosis. 255.255.255.255 is the broadcast address. In IPv6, ::1 is loopback and fe80:: is link-local.

IPv6 in brief

128 bits against IPv4’s 32, which is 340 undecillion addresses — enough that every device can have a globally routable one and network address translation becomes unnecessary. Written as eight groups of four hex digits, with one run of zero groups abbreviated to a double colon. Adoption passed 40% of Google’s traffic years ago and continues to climb, which is why any code parsing addresses should handle both families rather than assuming four dot-separated numbers.