Port check
Is a TCP port reachable from the internet? Test a server, or your own connection to confirm port forwarding.
Frequently asked questions
What is the difference between closed and filtered?
Closed means the host answered and refused the connection, so the host is reachable but nothing listens on that port. Filtered means no answer at all, usually because a firewall silently drops the packets.
My port forwarding does not work. What should I check?
Make sure the application is running and listening, the router forwards the port to the right local IP, the local firewall allows it, and your ISP does not use carrier-grade NAT — with CGNAT, incoming connections cannot reach you.
Can I check UDP ports?
No. UDP has no handshake, so an outside check cannot reliably tell open from filtered. This tool tests TCP ports.
Tools
DNS propagation checkerQuery resolvers around the world and the zone's authoritative nameservers in one go, and see on the map where your change has arrived.PingRound-trip time and packet loss from our server. Use TCP mode when a host drops ICMP.TracerouteThe path packets take from our server to the target, hop by hop, with the network (ASN) each router belongs to.SSL / TLS checkCertificate validity, chain, hostname match and which TLS versions the server accepts.HTTP headersFollow the redirect chain, see response headers and timing, and grade the security headers.WHOIS lookupRegistration details for a domain or the owner of an IP range, straight from the registry's WHOIS servers.Mail & blacklistMX, SPF, DMARC and DKIM for a domain, plus a check of its mail servers against public DNS blocklists.Subnet calculatorEnter an address with a prefix or a mask, for example 192.168.10.37/26 or 10.0.0.1 255.255.240.0.What is my IP?This is the address websites see when you connect to them.