port checker

Is my port open?

Check whether a TCP port is open on any public host. Useful for verifying firewall rules, port forwarding, and service reachability.

quick:

How the check works

When you enter a hostname and port, our server attempts a single TCP handshake against that public address. If the handshake completes, the port is open, a service is listening and reachable from the public internet. If the target refuses the connection or the packet is dropped inside the timeout, the port is closed. It is a targeted single-port check, this tool does not scan port ranges and does not test UDP.

Why a port might appear closed

  • The service is not listening on that port.
  • A firewall between our checker and the host is dropping the packet.
  • The host is behind NAT (typical for home routers), and the port has not been forwarded from the router to the internal machine.
  • The service is bound to 127.0.0.1 instead of a public interface, so it accepts only local connections.
  • The host uses an IP allowlist that excludes our checker.

Public reachability only

The check runs from our server, so it can only reach hosts with a public IP address. Private ranges, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, and 127.0.0.1, are not reachable from the public internet and are rejected. To verify a machine on your home or office network, you need to test from the same network.

Related: uptime checker for full-URL HTTP status, DNS lookup if the hostname does not resolve, and HTTP headers to see what a running web service is actually returning.

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AIExplain this port

Frequently asked

What does "open" vs "closed" actually mean?
Open means our server completed a TCP handshake with the target host and port, a service is listening and reachable from the public internet. Closed means the connection was actively refused, filtered by a firewall, or timed out. Open is not always desirable: an unexpected open port may indicate a service that should not be reachable.
Why does my port look closed when the service is running?
The most common reasons are (1) a firewall between us and the host is blocking that port, (2) the host is behind a NAT router and the port has not been forwarded from the router to the internal machine, (3) the service is bound to 127.0.0.1 instead of a public interface, or (4) the host uses an IP allowlist that excludes our checker.
Can I scan a range of ports or check UDP?
No. This tool performs a single TCP connection check to a single port at a time, no ranges, no UDP. That is intentional: running port scans without permission is often against acceptable-use policy, so the tool is scoped to targeted checks.
Can I check localhost or my home network?
No. The check runs from our server, so it can only reach hosts with a public IP address. Private ranges like 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, and 127.0.0.1 are not reachable from the public internet and are rejected.