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Port checker

Find out whether a port on your connection can be reached from the internet. This is how you confirm port forwarding works.

One port, or up to 10 separated by commas.
Or pick a common set
Enter an address and a port to test it.

To test port forwarding, press Use my address, enter the port you forwarded, and make sure the program that listens on it is running. A port with nothing listening reports as closed even when forwarding is correct.

What the three results mean

Our probe opens a TCP connection to each port from outside your network and reports what happened.

ResultWhat happenedUsual cause
OpenSomething accepted the connectionForwarding works and a program is listening
ClosedThe device answered and refusedThe port reaches a device, but nothing is listening on it
FilteredNo reply before the timeoutA firewall or router dropped the packet, or the provider blocks the port

When a forwarded port still shows closed

  • Nothing is listening. Start the game server, camera or application first. Forwarding to a port with no program behind it looks closed.
  • The device firewall blocks it. Windows Defender Firewall and macOS both block inbound connections until you allow the program.
  • The rule points at an old address. If the device got a new local address from the router, the rule now points at nothing. Reserve its address in the router's DHCP settings.
  • You are behind carrier-grade NAT. If your router's WAN address starts with 100.64 to 100.127, or differs from the address shown on this page, your provider shares one public address among many customers and inbound ports cannot reach you. Ask the provider for a public address.
  • Your provider blocks the port. Residential connections often have 25, 80, 135 to 139 and 445 blocked.

Ports people check most

PortServiceUsed for
22SSHSecure remote shell and file transfer
80 / 443HTTP / HTTPSWeb servers
3389RDPWindows Remote Desktop
25565MinecraftJava Edition game server
32400PlexMedia server remote access
51820WireGuardVPN (UDP, which this TCP check cannot see)

Only test addresses you own or have permission to test. Each check is limited to ten ports.

Common questions

Is an open port dangerous?

An open port is only as safe as the program behind it. Keep that software updated, require strong credentials, and close anything you no longer use. Remote Desktop and database ports should not be open to the whole internet.

Can this check UDP ports?

No. UDP has no handshake, so an outside probe cannot reliably tell open from filtered. Test UDP services by connecting with the real client from another network.

Why does the same port show open from inside my network?

Tests from inside your network never cross the router's firewall. Only a check from the internet, like this one, shows what outsiders can reach.