IP Address Info

An IPv4 address is a 32-bit number, usually written as four dotted octets, but it is also a single integer and a specific point in the global address plan. This tool decomposes an address into its class, its scope (public, private, loopback, link-local, multicast, or reserved), its decimal/hexadecimal/binary forms, and the reverse-DNS pointer name used for PTR lookups.

What the fields tell you. The legacy class (A/B/C/D/E) comes from the first octet and still shows up in documentation and tooling, even though routing has been classless since CIDR. The scope is the operationally important part: 10.x, 172.16–31.x, and 192.168.x are RFC 1918 private space that is not routable on the internet; 127.x is loopback; 169.254.x is link-local (an address a host self-assigns when DHCP fails); 224–239.x is multicast. The reverse pointer (9.5.0.10.in-addr.arpa) is the name you would query to map the address back to a hostname.

How you'll use it. During reconnaissance or triage, quickly classify an address: is this internal or internet-facing? Is a "server IP" in a log actually a link-local artifact? The radix conversions are handy when an address appears in a non-dotted form — some obfuscation and SSRF payloads express 127.0.0.1 as its decimal integer (2130706433) or in hex to slip past naive blocklists.

Common mistake. Assuming a private-looking address is harmless. Server-Side Request Forgery frequently targets exactly these ranges — 169.254.169.254 is the cloud metadata endpoint, and internal 10.x/192.168.x services are the SSRF attacker's goal. Seeing the scope makes those targets obvious. A second trap is trusting the textual form of an address: 127.0.0.1, 0177.0.0.1 (octal), 0x7f.1, and the bare integer 2130706433 all resolve to loopback, and a blocklist that matches only the dotted-decimal string waves the others straight through. The radix conversions here exist precisely so you can normalise before comparing.

Defensive angle. When validating user-supplied hosts or URLs (webhooks, image fetchers, "import from URL" features), resolve and normalize the address, then reject private, loopback, link-local, and reserved ranges — and re-check after DNS resolution to defeat rebinding. This tool shows exactly the categories your allowlist/denylist must account for, including the alternate integer and hex encodings attackers use to bypass string-based filters. Use the subnet calculator to define those ranges precisely as CIDR blocks, and the DNS record explainer when a hostname resolves somewhere you did not expect.