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Open port checker
See which ports on your connection, or on a server you manage, can be reached from the internet.
An open port checker tests whether TCP ports on an IP address or domain can be reached from the internet. Enter up to ten ports; each is tried from Cloudflare's edge and reported as Open, Closed, No reply or Not tested. It is free, and the hosts and ports you test are not stored.
We don't store the hosts or ports you test.
What open, closed and no reply mean
- Open — a service accepted the connection.
- Closed — the host replied, but nothing is listening on that port.
- No reply — nothing came back within 5 seconds; a firewall probably drops the request.
- Not tested — we couldn't test it from here (port 25, a private address or Cloudflare's network).
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How it works
What this port checker tells you
What we test
Enter an IP address or a domain and up to ten ports. For each port we open a TCP connection from Cloudflare's edge, the way any computer on the internet would, and close it as soon as it is answered. Nothing is sent over the connection. When you enter a domain, we look up its address first and show which IP was tested.
| Result | What it means |
|---|---|
| Open | A program on the host accepted the connection: a web server on 80 or 443, SSH on 22, remote desktop on 3389, a proxy on 1080, 3128 or 8080. |
| Closed | The host answered but refused, because nothing listens on that port. |
| No reply | Nothing came back within 5 seconds. Usually a firewall silently drops the attempt; sometimes the host is simply offline. |
| Not tested | Port 25, private addresses and hosts on Cloudflare's own network can't be tested from here. They are never reported as Closed. |
Why a port shows closed while your program runs
Most home and office connections sit behind a router. The router holds the public IP you see here, and it passes nothing inward unless you set up port forwarding, so a service on your computer shows as closed or no reply. Many internet providers also share one public IP between several customers (carrier-grade NAT); then port forwarding cannot work at all. Check the forwarding rule on the router, the firewall on the computer or the server's security group, and that the program listens on all interfaces rather than only on 127.0.0.1.
Limits and fair use
The test runs from a Cloudflare data center, not from your computer, so it shows what the rest of the internet sees. Port 25 (email) can't be tested, because Cloudflare blocks outgoing connections to it. Hosts on Cloudflare's own network can't be tested either: our tester runs on Cloudflare, so those ports are marked Not tested, never Closed. Private and reserved addresses such as 192.168.x.x or 10.x.x.x are refused, since the internet can't reach them. Port ranges aren't supported, and one network can test up to 60 ports an hour. Only test hosts you own or are allowed to test. To see whether your IP looks like a datacenter or an ISP network, use the IP quality check.
FAQ
Questions about the port checker
Why is my port closed when the program is running?
The connection from the internet stops before it reaches the program. The usual causes are a router without a port forwarding rule, a firewall on the computer or server, an internet provider that shares your public IP between customers, or a program that only listens on 127.0.0.1. Fix them in that order and check again.
What's the difference between Closed and No reply?
Closed means the host answered and refused the connection: it is online, but nothing listens on that port. No reply means nothing answered within 5 seconds. That usually points to a firewall dropping the request, but the host may also be offline.
Can I check any IP address or domain?
Any public IP address or domain, up to ten ports per check and 60 ports an hour from one network. Private and reserved addresses are refused, port 25 can't be tested, and hosts on Cloudflare's network show as Not tested. Please only test hosts you own or are allowed to test.
Do you keep what I test?
No. The host and ports are tested once and the result is shown back to you. We don't save them or write them to logs. We only count how many ports a network checks, under a one-way hash of its IP, to keep the tool free of abuse.