IP Subnet Validator
Check an IPv4 or IPv6 address or CIDR subnet. Get a clear explanation if something isn't right.
One box for IPv4 and IPv6. CIDR prefixes are optional. Results update as you type.
How subnet validation works
An IP address can be valid without being a valid subnet starting address. For example, 192.168.1.219/26 is a valid host address, but the subnet starts at 192.168.1.192/26. This checker shows the correct network and explains the difference.
What is CIDR?
The number after the slash specifies how many leading bits identify the network. IPv4 supports /0 through /32; IPv6 supports /0 through /128. If no prefix is entered, a single IPv4 address is treated as /32 and a single IPv6 address as /128.
All calculations happen in your browser. Entered IP addresses are not sent to a validation server.