PORT SCANNER
Open Port Checker
We scan common ports on your current public IP. An open port may mean a service is reachable from the internet.
Checking open ports…
What is an open port?
A port is a numbered door on your connection that a specific service listens on — 80 and 443 for web servers, 22 for SSH, 3389 for Windows Remote Desktop, and so on. An “open” port means something on your IP is reachable from the public internet on that number. That’s required for hosting a server or making port forwarding work, but every open port is also a door an attacker can knock on. This checker scans your IP from the outside and reports which common ports answer.
FAQ
What is port forwarding and how do I test it?
Port forwarding tells your router to send incoming traffic on a given port to a specific device on your network — needed for game servers, hosting, remote desktop or some torrent setups. To test it: set up the forward in your router, start the service that should listen on that port, then run this checker. If the port shows “open”, forwarding works; if it shows “closed”, the router rule, a firewall, or your ISP is blocking it.
Which ports are risky to leave open?
3389 (Remote Desktop), 22 (SSH), 445 (SMB file sharing), 23 (Telnet) and database ports like 3306 (MySQL) are frequent attack targets and should never be open to the whole internet without a firewall or VPN in front. Web ports 80/443 are normal for a server but pointless to expose on a home connection.
Why is a port closed when I expected it open?
Usually one of: no service is actually listening on it, your router isn’t forwarding it, a local or router firewall blocks it, or your ISP filters it (many block 25, 80 and 445 on home plans). CGNAT — where your ISP shares one public IP among many customers — also makes inbound ports impossible without extra setup.
Does a closed port mean I’m safe?
Closed is the safer default — nothing is reachable there. But security isn’t only about ports: outbound connections, your browser fingerprint and DNS behaviour matter too. A clean port scan is good, not a full guarantee.
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