Question 1

What is CIDR?

Accepted Answer

Classless Inter-Domain Routing (CIDR) writes an IP network as an address plus a prefix length, like 10.0.0.0/24. The number after the slash is how many bits belong to the network.

Question 2

Does dickencidr support IPv6?

Accepted Answer

Yes. Switch to IPv6, enter an address or prefix such as 2001:db8::/32, and see network bounds, compressed and expanded forms, and address count.

Question 3

Is my data sent to a server?

Accepted Answer

No. All CIDR calculations run in your browser. Addresses and prefixes never leave your device.

Prefix	Mask	Addresses	Usable
/8	255.0.0.0	16,777,216	16,777,214
/16	255.255.0.0	65,536	65,534
/20	255.255.240.0	4,096	4,094
/24	255.255.255.0	256	254
/25	255.255.255.128	128	126
/26	255.255.255.192	64	62
/27	255.255.255.224	32	30
/28	255.255.255.240	16	14
/29	255.255.255.248	8	6
/30	255.255.255.252	4	2
/31	255.255.255.254	2	2
/32	255.255.255.255	1	1