CIDR calculator

For example 192.168.1.0/24, 10.0.0.0 255.0.0.0 or 2a01:e0a::/29. This tool contacts nothing: private addresses are expected here.

About Privacy Domain diagnostics: dnstools.oxmo.org Geolocation: local GeoLite2 databases, refreshed weekly. No request ever leaves for a third party.