Is it safe to run this check from a public tool?

This check simply attempts a standard TCP connection, the same kind any visiting browser or client would make — it doesn't probe for vulnerabilities or attempt unauthorized access. It only tells you whether a connection can be established, which is information already visible to anyone on the internet who tries to connect.

Why does the check run from your servers and not my browser?

Browsers can't make raw TCP connections to arbitrary ports for security reasons, so this check runs server-side instead, giving an accurate result regardless of what's blocked in a browser sandbox.

Hostperl DNS Tools

Port Checker

Check whether a TCP port is open or closed on a given hostname or IP address, run securely from our servers.

Use this to confirm whether a service is actually reachable on the network, separate from whether it's running locally on the server. Common for diagnosing firewall and security group issues.

Frequently asked questions

A firewall on the server, network, or cloud provider's security group can block a port even if the service behind it is running correctly. Double-check firewall rules and security group settings if a port you expect to be open shows as closed here.