Free Online Port Scanner
Run a TCP connect scan against selected ports on a public host to confirm whether expected services are reachable from the internet.
Common use cases
- Verify that web, mail, SSH, DNS, or database ports are open or closed as expected.
- Check firewall changes after deployment without installing scanner software.
- Identify accidentally exposed services that need to be restricted.
Frequently asked questions
Which ports can I scan?
Enter a comma-separated list of TCP ports in the scanner form, such as 22,80,443.
Can I scan private IP ranges?
No. NerdTools validates targets so scans stay limited to public hosts and public IP addresses.