How is the IP class determined?

It is read from the first octet — 0–127 is Class A, 128–191 is Class B, 192–223 is Class C, 224–239 is Class D (multicast) and 240–255 is Class E (reserved).

Which ranges are private?

Per RFC 1918 the private ranges are 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. 127.0.0.0/8 is loopback and 169.254.0.0/16 is link-local. Everything else is treated as public.

Are IP classes still used?

Classful addressing has largely been replaced by CIDR for routing, but the A–E classes and default masks are still taught and referenced. The scope check (public vs private) remains practically important.

IP Class Finder

Find the class (A–E) and scope of any IPv4 address.

Identify the class and scope of an IPv4 address

Enter any IPv4 address to find its classful range (A, B, C, D or E), the default mask for that class, its typical use, and its scope — public, RFC 1918 private, loopback, or link-local.

Class is determined from the first octet, and the scope check applies the standard reserved ranges. All analysis runs in your browser.