Network Security & Subnet Tools

Network, broadcast, mask and usable range for any block — and split it into subnets.

Enter an IPv4 address with a prefix or subnet mask, see the whole subnet, and divide it.

Convert between a start-end IP range and the CIDR blocks covering it.

Find which blocks in a list overlap, contain or duplicate each other.

Expand, compress and inspect an IPv6 address or prefix.

Every representation of an address at once — dotted, binary, integer and hex.

Tell whether an address is routable, private, loopback or otherwise reserved.

Look up what normally listens on a TCP or UDP port, and why it matters if it is exposed.

What a status code means, which RFC defines it, and what to do next.

Query A, AAAA, MX, TXT, NS, CNAME, SOA and CAA records for any domain.

Registrar, registration and expiry dates, status codes and name servers for any domain.

Check whether one well-known port on a host answers — open, closed, or timed out.

Every certificate publicly logged for a domain, decoded — via Certificate Transparency, not a live handshake.