Open Port Check
Test whether a TCP port is open and reachable on your IP or any host.
No results yet
Enter a host above and press Run to start the check.
About the Open Port Check
Use this port forwarding tester to check whether a specific TCP port is open and reachable from the public internet on your own IP address or any host. It's the fastest way to confirm your router's port forwarding is working, host a game or web server, or troubleshoot a firewall — the check runs from our server to the host and port you specify, so it tests real inbound reachability the same way an outside user would reach you.
How to use
- Your public IP is filled in automatically (or enter any host).
- Enter the TCP port number to test (e.g. 25565 for Minecraft, 80 for HTTP).
- Press Run to see whether the port is open from outside.
What an open, closed and filtered result each mean
This check opens a real TCP connection from our server to the host and port you name, so it answers one specific question: is that port reachable from the public internet? That is exactly the question you want when verifying a port forward, a firewall rule or a newly exposed service — and it is a different question from whether the port is open on your local machine, which a tool running on your own network cannot distinguish.
Three outcomes, and the difference between the last two is diagnostic. **Open** means the TCP handshake completed: something is listening and accepting. **Closed** means the host answered with an RST — it is reachable, but nothing is bound to that port, so your service is not running or is listening on a different interface. **Filtered** means nothing answered at all before the timeout: a firewall is dropping the packet silently, which is the normal configuration for a well-defended host.
A filtered result on a port you just forwarded usually means the traffic is not reaching the machine you think it is. The common causes, in the order worth checking: the router forwarded to a stale internal IP after DHCP reassigned it; the host's own firewall is dropping the connection after the router passed it along; or your ISP is using CGNAT, in which case your router's WAN address is not the address the internet sees and no port forward will ever be reachable. Comparing your router's WAN IP to your public IP settles the last one immediately.
Frequently asked questions
- How do I test if port forwarding is working?
- Set up the forwarding rule on your router, start the service on your device, then enter your public IP (pre-filled here) and the forwarded port and press Run. If it shows open, the port is reachable from the internet and forwarding is working. If it shows closed, see the reasons below.
- Why does my port show as closed?
- Common reasons: no service is listening on that port, a firewall is blocking it, port forwarding isn't configured (or points to the wrong device) on your router, you're behind CGNAT so your router's WAN IP isn't your public IP, or your ISP blocks the port.
- Can I check a port on my own connection?
- Yes — your public IP is pre-filled. Make sure a service is actually listening and your router forwards the port to your device, then test it here.