Port Scanner
Check which ports are open on any public IP address or domain. Scans 21 common ports instantly.
Frequently Asked Questions
Is port scanning legal?
Port scanning your own servers is always legal. Scanning third-party servers without permission may violate computer crime laws in many jurisdictions. Only scan hosts you own or have explicit written permission to test.
What does an open port mean?
An open port means a service is actively listening for connections on that port. Open ports on public servers are not necessarily dangerous — a web server needs port 80 and 443 open. Concern arises when unexpected ports like 3306 (MySQL) or 27017 (MongoDB) are open to the public internet.
Why are some ports showing as closed when they should be open?
Firewalls and security groups block connection attempts without sending a response. Our scanner uses TCP connect with a 1.5s timeout — firewalled ports appear closed even if a service is running behind them.