Free · No sign-up · Real TCP connect scan
Check which ports are open, closed or filtered on any host — free, instant, right from your browser.
Enter a host you have permission to scan and choose port categories or custom ranges.
Our server attempts a real TCP connection to every port, concurrently.
View each port as open, closed or filtered, with the likely service running on it.
Something is actively listening on this port and accepted our connection.
The host is reachable but nothing is listening — the connection was refused.
No response at all — usually a firewall silently dropping the connection.
It tries to open a TCP connection to each port on a host. If the connection succeeds the port is open, if it's actively refused it's closed, and if there's no response at all it's usually filtered by a firewall.
Scanning hosts you own or have explicit permission to test is standard security practice. Scanning third-party systems without permission can violate their terms of service or local law — only scan hosts you're authorized to test.
Filtered means our connection attempt got no response at all — usually because a firewall is silently dropping the packets rather than actively refusing the connection.
We cap each scan at 50 ports and rate-limit requests to keep the tool fast and fair for everyone, and to prevent it being used to scan large ranges on hosts that haven't agreed to be tested.
Not by itself — plenty of open ports (like 443 for HTTPS) are supposed to be open. What matters is whether each open port is running something you intend to expose, and whether it's properly secured and up to date.