Enter a domain and run a lookup to see results.
Port Check
Check if common ports are open on any host. TCP connection test to diagnose firewall status.
Detected
—
Tool Features
Related Guides
Coming Soon Open ports are checked per server in attack surface management (Business plan).
Open Port Scanner
Check common TCP ports on any host to see which services answer. The default list covers FTP (21), SSH (22), SMTP (25), DNS (53), HTTP/HTTPS (80/443 and 8080/8443), mail (POP3, IMAP and their TLS ports), MySQL (3306), PostgreSQL (5432) and RDP (3389). Each result shows the port, service name and response time. Open ports show the attack surface of a host — check only hosts you are allowed to test.
How It Works
TCP connections are opened from Cloudflare Workers to each port. Open means the connection was established within 3 seconds. Refused, reset or silent ports all show as Closed — from outside we cannot tell a closed port from a firewalled one. Other connection errors are counted separately as No answer. Workers cannot connect to Cloudflare's own IP ranges, so a host behind Cloudflare is reported as not checkable rather than all closed.
FAQ
Is port scanning legal?
Scanning your own servers is always legal. Scanning third-party systems without authorization may violate computer misuse laws in many jurisdictions. This tool is intended for authorized security testing, penetration testing engagements, and educational purposes only.
What are the most commonly targeted ports?
SSH (22), HTTP (80), HTTPS (443), RDP (3389), SMB (445), and database ports (3306 MySQL, 5432 PostgreSQL, 27017 MongoDB) are frequently probed. Leaving these open to the internet without proper authentication creates significant security risk.
Why is there no "filtered" status?
A firewall that silently drops packets and a port that refuses the connection look the same to this tool: neither ends in an open connection, so both show as Closed. Telling them apart needs raw packet scanning, which this tool does not do. If a port you expect to be open shows Closed, check the firewall or security group first, then whether the service is actually listening.