Open port checker

Closed means your router or device answered and refused the connection, so the address is reachable but nothing listens on that port. Filtered means nothing answered at all within three seconds, which is what a firewall that silently drops traffic looks like. Both keep the port unreachable.

A tool that probes any address someone types can be used to scan other people's networks. This checker only tests the IP your request comes from, so you can only ever check your own connection. To test a proxy from the outside, use our proxy checker instead.

The usual causes are: the service isn't running or only listens on localhost; the forwarding rule points to an old local IP after DHCP gave your computer a new one; a firewall on the computer blocks the port; your provider puts you behind carrier-grade NAT, so the router has no public IP of its own; or your provider blocks the port.

Compare the WAN or internet IP in your router's status page with the IP shown here. If the router shows an address from 100.64.0.0 to 100.127.255.255, or any address that differs from the one here, your provider shares one public IP between customers and incoming port forwarding won't work without their help.

No, it tests TCP only. UDP has no handshake, so a closed UDP port and a silent service look the same from the outside. Many games and VPNs use UDP; check those from the application itself.

The checker tests the IP your request arrives from. Behind a proxy or VPN that is the proxy's or VPN's exit address, not your home connection, so the result describes their server. Turn the proxy off to test your own ports.

Yes. Our server makes one TCP connection per port and closes it as soon as the handshake completes, without sending any data. The IP and ports are not stored or logged, and each visitor can run a handful of checks per minute.