How to use the IP Address Class Finder
- 1. Paste addressesOne per line, or separated by spaces or commas.
- 2. Find classSee each address's class, default mask, type and leading bits.
- 3. Read the summaryCount private and public addresses at a glance.
Classes and types
Before CIDR (1993), the first bits of an address fixed its class: A starts with 0 (first octet 0–127, default /8), B with 10 (128–191, /16), C with 110 (192–223, /24), D with 1110 (224–239, multicast) and E with 1111 (240–255, reserved). Classes no longer decide routing, but exams and some tools still use them. Everything is calculated in your browser; nothing you enter is uploaded.
More useful today is the address type. The tool recognises private ranges (RFC 1918), loopback (127.0.0.0/8), link-local (169.254.0.0/16, used when DHCP fails), carrier-grade NAT (100.64.0.0/10, common with Indian mobile and broadband providers), documentation and benchmark ranges, multicast and reserved blocks; anything else is public.
Worked example
The sample list of 9 addresses covers all five classes. 10.25.4.7, 172.20.1.1 and 192.168.1.10 are private, in classes A, B and C. 8.8.8.8 is a public class A address, 127.0.0.1 is loopback, 169.254.10.20 is link-local, 100.72.3.4 is carrier-grade NAT, 224.0.0.251 is class D multicast, and 250.1.1.1 is class E. The summary shows 3 private and 1 public.
Exam tips
- 127.x.x.x is technically class A but reserved for loopback, so class A networks run 1 to 126.
- 172.16 to 172.31 is private; 172.32 is public.
- We checked 20 edge addresses, such as 100.63.255.255 (public) and 100.64.0.1 (CGNAT).
Frequently asked questions
Is 0.0.0.0 a valid address?
It means "this network" or "any address" when software listens; you can't assign it to a device.
Does it handle IPv6?
IPv6 has no classes. Use our subnet calculator to see an IPv6 address's type.
Is the IP class finder free?
Yes. You can open the IP class finder and use every option without signing up. When you check addresses for the first time, we ask once for your name and WhatsApp number; after that it, and every other Uncodemy tool, opens straight away.