Open Port Checker
This free open port checker tests whether a port on your own internet connection accepts connections from the internet, one port at a time or 10 common ports at once.
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How the port check works
We try to connect to your IP address on the port you pick, from our server in Germany. If something answers, the port is open. If your router or firewall refuses, it's closed. If nothing comes back within 3 seconds, it's filtered.
The tool only ever checks the address you're visiting from. You can't use it to scan someone else's network.
Open, closed or filtered?
Open means a program on your network accepts connections from anywhere on the internet. That's what you want for a game server or a web server, and for nothing else.
Closed and filtered both mean the port is shut from outside. Filtered usually means a firewall silently drops the attempt, which is the safest setting for anything you don't need to share.
Ports you shouldn't leave open
Databases (MySQL 3306, PostgreSQL 5432, Redis 6379, MongoDB 27017) and Remote Desktop (3389) are scanned constantly by attackers. Keep them behind a firewall or a VPN.
If you need to reach them from outside, open them only to your own IP address, or connect through a VPN or an SSH tunnel.
Frequently asked questions
Why is my port closed even though I forwarded it?
Check that the program is running and listening, that the forwarding rule points at the right device's local IP address, and that the computer's own firewall allows the port. Some providers also block ports or put you behind a shared address (CGNAT), where port forwarding can't work.
Can I check someone else's IP address?
No. The checker only tests the address you're visiting from, so it can't be used to scan other people's networks.
Why doesn't it work over IPv6?
Our checking server only uses IPv4 for now. If you're connected over IPv6, switch to IPv4 (for example on mobile data, or with IPv6 turned off) and try again.
Which ports are in the common set?
22 (SSH), 25 (SMTP), 80 (HTTP), 443 (HTTPS), 587 (mail submission), 993 (IMAPS), 3306 (MySQL), 3389 (Remote Desktop), 8080 and 8443 (web alternatives). They're the ports people most often open, on purpose or by accident.
How often can I run a check?
Each visitor can run 2 checks a minute and 10 an hour. A check of the 10 common ports counts as one.