Work out a subnet from a CIDR or an address plus dotted mask: network, netmask, wildcard, broadcast, usable host range and counts. IPv4 and IPv6. Handles /31 point-to-point and /32 host routes correctly.

Check whether an IP address falls inside a CIDR block, and show that block's first-to-last range. IPv4 and IPv6.

Convert an IPv4 address between dotted decimal, unsigned 32-bit integer, hex and dotted binary. Accepts any of the four as input.

Show the fully expanded form and the correct RFC 5952 compressed form of an IPv6 address, plus what kind of address it is (global, ULA, link-local, loopback, documentation…).

Identify the vendor behind a MAC address from the full IEEE MA-L registry (about 40,000 assignments, bundled — no network), and decode the multicast and locally-administered bits. Explains randomised/privacy MACs.

What runs on a port and whether it is safe to expose. Covers the 100 ports whatismynetip.com documents by hand: service, protocols, category, common software, an exposure verdict (never / caution / normal) with the reasoning, and related ports. Give a port number, or a query like 'redis' or 'wireguard' to search by service. detail:true adds the full explainer and FAQ.

Resolve a DNS name over DNS-over-HTTPS. Record types: A, AAAA, MX, TXT, NS, CNAME, CAA, SOA, PTR, SRV. Returns every answer with its TTL, and says why when there is none (NXDOMAIN vs no record of that type).

PTR lookup for an IPv4 or IPv6 address — what name the address maps back to, if any.

Check an IPv4 address against five common spam/abuse blocklists (Spamhaus ZEN, SpamCop, SORBS, Barracuda, s5h). Honest about lists that refuse public-resolver queries — those come back n/a, never a false 'clean'.

Connect to a public host and report the TLS certificate it actually serves: subject, issuer, validity window and days left, SANs, protocol and cipher, whether the chain verifies, and the SHA-256 fingerprint. Any port (default 443). Accepts a URL. Refuses hosts that resolve to private or reserved addresses.

The public IP address the internet sees this machine as, with the edge location that saw it, reverse DNS, the network's ASN and organisation, and a datacenter/VPN hint. Needs an outside observer, so this one talks to Cloudflare's trace endpoint and Team Cymru's ASN DNS.