IPv4 Address Converter

Enter an IPv4 address in any common form — dotted-decimal (192.168.1.1), a 32-bit integer (3232235777) or hex (0xC0A80101) — and this tool shows all of them at once, plus the binary octets. It also classifies the address: private, public, loopback, link-local, multicast, broadcast, shared (CGNAT) or reserved. Useful for firewall and ACL rules, database storage (IPs are often kept as integers), log parsing and learning how addresses map to numbers. Everything is computed locally in your browser.

The integer form is the one worth storing, and the reason is size rather than elegance. An IPv4 address is exactly 32 bits, so it fits an unsigned integer column in four bytes, while the dotted string takes up to fifteen and cannot be compared or ranged without parsing. A firewall rule asking whether an address falls inside a block is an integer comparison once both sides are numbers, and a string comparison gets it wrong the moment the octets have different digit counts.

Signed storage is where this goes wrong in practice. Anything from 128.0.0.0 upward has the top bit set, so a signed 32-bit column stores it as a negative number and every naive range query against it fails. That is half the address space, and the bug hides until the day a user turns up on a high address.

Dotted-decimal is more permissive than people expect. The traditional parser accepts fewer than four parts, treating the last as the remainder, and reads a leading zero as octal, so 010.1 is a legal way to write 8.0.0.1 and 127.1 is a legal way to write 127.0.0.1. Modern libraries mostly reject these, but not all of them do, and the mismatch between two parsers on the same string has been the basis of real access-control bypasses.

The classification comes from the reserved-range registry rather than from anything in the number, and those ranges have been added to. 100.64.0.0/10 for carrier-grade NAT arrived in 2012, which is recent enough that older tools report it as ordinary public space.