Open Port Checker

Understanding whether a port is reachable from the outside world is a fundamental task for network administrators, developers, and even gamers. When you host a service—be it a web server, a game lobby, or a VPN—that service “listens” on a specific port. If your router's firewall or your ISP blocks that port, external users won't be able to connect.

Our Open Port Checker allows you to remotely verify your public IP address and test specific ports without needing complex software. This is particularly useful for debugging Port Forwarding issues. If you've set up a rule in your router but the port still shows as “Closed” or “Filtered,” you know the issue lies either in the router configuration, the local firewall (like Windows Defender), or the service itself not running correctly.

Before running a scan, it's often helpful to perform an IP Lookup to ensure you are targeting the correct machine, or use our DNS Lookup tool if you are checking a domain name instead of a literal IP address.

If our tool reports that a port is closed but you expect it to be open, check the following common roadblocks:

1. Service Status: Ensure the software or service (like a web server or game) is actually running and listening for connections on that specific port.
2. Local Firewall: Check Windows Firewall or ufw on Linux. You must create an “Inbound Rule” to allow traffic on that port.
3. Router Port Forwarding: Access your router settings and ensure the external port is mapped to the correct internal private IP address of your machine.
4. CGNAT or ISP Blocking: Some ISPs use Carrier-Grade NAT, which prevents traditional port forwarding. Additionally, some ISPs block common ports like 80 or 25 to prevent users from running servers on residential lines.

If your network seems slow while testing, you might want to use our Network Latency Monitor to check for packet loss or high ping during the connection attempt.