CIDR stands for Classless Inter-Domain Routing, and refers to the standard of dividing the entire IP address space into smaller networks of variable size. A CIDR IP address looks like a normal IP address except that it ends with a slash followed by a number, called the IP network prefix, for example 192.168.2.0/24. The tools on this website allow you to find the first and last IP addresses within a CIDR, check whether a specific IP address is within a CIDR, and get the CIDR from an IP address range.
Convert CIDR to IP Addresses
Check for an IP Address in a CIDR
Convert an IP Range to CIDRs