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Port Checker

Find out whether a TCP port is open and reachable from the internet. Pick a common port or enter any port from 1 to 65535.

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What this tool does

The port check tries to open a TCP connection, from our server, to the address and port you choose. If the connection is accepted, the port is open and reachable from the internet. It is the fastest way to find out whether your router's port forwarding worked, whether a game server is visible to your friends, or whether the firewall is letting a service through.

The field is prefilled with your public IP. To test a server, replace it with that server's IP or domain.

How to read the result

  • Open: a program is listening on the port and nothing along the way is blocking it.
  • Closed: the address responded but refused the connection. Usually the program is not running or is not listening on that port.
  • No response: nothing came back within 3 seconds. This is typical of a firewall silently dropping the connection, or of a device that is turned off.

Why the port won't open

Missing port forwarding on the router. For a service at home to be visible, the router has to forward the port to the internal IP of the computer or console.

System firewall. Windows and many antivirus programs block incoming connections. Allow the program or the port.

CGNAT. If your public IP starts with 100.64 through 100.127, or if your router's IP differs from the one shown here, your ISP shares the IP among customers and ports cannot be opened. Ask your ISP for a public or static IP.

ISP blocking. Some ISPs block ports such as 25 and 80 on residential connections.

Responsible use

Only test addresses you own or are authorized to check. The tool tests one port at a time, from a fixed list, and has usage limits per person and per address. Internal network addresses are not tested.

Frequently asked questions

How do I know if my port is open?

Pick the port from the list, keep your IP in the field and click Check port. If the result is Open, the port is reachable from the internet.

Why does the port show as closed if I already opened it on the router?

Make sure the program is running and listening on the port, that the computer's firewall allows the connection and that your connection is not behind CGNAT.

What is the difference between closed and no response?

Closed means the address refused the connection. No response means nothing came back, which usually points to a firewall dropping the packets.

Can I test any port?

We test a list of common ports, such as 80, 443, 22, 3389 and 25565, one at a time. Scanning every port is not allowed.

Does the tool test UDP ports?

No. TCP only. A UDP test does not give reliable results without a specific service answering.