Support NetworkCalc
Free tools, kept free and independent by the people who find them useful.
NetworkCalc is a free suite of network tools and APIs — subnet calculation, DNS lookups, security checks, and more — built for anyone who needs quick, reliable answers. The core web tools and public APIs need no account and no payment.
The project is independently built and maintained by Matthew Fisher. NetworkCalc Pro adds domain monitoring, alerts, and reports for people who want them (see Pro), but the core web tools and public APIs stay free for everyone. Donations are what keep them that way.
The public APIs are actively maintained, but offered without a formal uptime SLA. If something looks broken, check the release notes or reach out.