Open Port Checker — Free & Instant

About this tool. Opens a raw TCP connection to any host and port from our edge and times the handshake. Handy for checking whether a service is reachable at all. Ports 80/443 are reserved for the HTTP checks, and port 25 is blocked platform-wide — the SMTP tool covers mail servers.

Ten signals decide whether your mail arrives. You just checked one.

An open port proves something is listening. Whether mail from that host is accepted by anyone else depends on records that have nothing to do with the port.

SPF, DKIM, DMARC, MX and blocklist status, graded A to F in one pass
Every problem written out in plain English, with the record to publish
Saved under Reports, so you can re-run it and see what changed
One domain watched against the blocklists daily

Run the full checkup free

No card, and nothing to cancel.

How to read your Open Port results

We open a TCP connection to the host and port you give and report whether it is open and how quickly it responds.
Open means something is listening. Closed or timed out means nothing is answering, or a firewall is blocking it.

Common problems and how to fix them

A service should be reachable but the port is closed

Check the service is running and bound to the right interface, and that no firewall or security group blocks the port.

HTTP Check HTTPS Check SMTP Test Latency Test Full email checkup

Common questions.

What does a port test do?

It checks whether a specific TCP port on a host accepts connections, and measures the connect time.

Why is a port showing as closed?

Either nothing is listening on that port, or a firewall is dropping the connection before it completes.