Open port checker

Our server tries to connect to the port you choose on your public IP, just as any computer on the Internet would. This lets you check whether you have correctly opened a port on your router for a server, a camera, a game or remote desktop.

What is an open port?

Ports let a single machine offer several services at once: the web uses 80 and 443, SSH 22, Windows Remote Desktop 3389… A port is open when a program is listening on it and connections from the Internet reach it.

At home, the router acts as a barrier (NAT): by default none of your devices' ports are reachable from outside. To publish a service you need a port forwarding rule on the router that sends that port to the device's local IP.

Why it may show as closed even though you opened it

The most common causes are: the program is not running or listens on another port; the Windows, macOS or Linux firewall blocks the connection; the router rule points to an old local IP (it is a good idea to reserve it via DHCP); or your ISP uses CG-NAT, sharing one public IP among several customers, in which case ports cannot be opened. If your router's IP does not match the one shown on this page, you are probably behind CG-NAT.

This tool only checks TCP ports and only the IP you are visiting us from (if you browse over IPv6, your IPv6 address is checked).

Is it safe to have open ports?

Every open port is a way in. Open them only when you need them, keep the software listening on them up to date and avoid exposing sensitive services such as remote desktop (3389), databases (3306, 5432) or admin panels to the Internet: use a VPN instead.