Result
Enter a port
Type one port, or up to 10 separated by commas, or pick a common port below. Only your own IP address can be checked.
Common ports
Click a port to check it. These are the default ports; if you changed the port in your app or game server, check that number instead.
Games
Remote access
Web and file servers
NAS, media and cameras
Downloads
Is your IP shared (CGNAT)?
Many providers, especially mobile and fiber ones, put several customers behind one public IP (carrier-grade NAT). Port forwarding then can't work. Open your router's status page, find its WAN or internet IP address and enter it here to compare.
Your connection
- IP address checked
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- IP version
- Checking…
- Your network
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What an open port means
A port is a numbered door on your IP address. Programs that accept connections from the internet, such as a game server, Remote Desktop or a NAS, each listen on their own port, like 25565 for Minecraft or 3389 for Remote Desktop.
A port is open when a connection from outside reaches a program that answers. At home, your router blocks all incoming connections by default. Port forwarding is the router rule that sends one port on to a device in your network.
How to open a port with port forwarding
- Give the device a fixed local IP address, for example in the router's DHCP settings.
- Open your router's admin page (often 192.168.0.1 or 192.168.1.1) and find Port Forwarding, Virtual Server or NAT.
- Add a rule: the external port, the device's local IP and the same internal port, protocol TCP (or TCP and UDP).
- Allow the port in the device's own firewall, such as Windows Defender Firewall.
- Start the program or server, then check the port here.
Why a port shows as closed
- The program isn't running, or it listens on a different port.
- The forwarding rule points to the wrong local IP, often because the device got a new address.
- Windows Firewall or a security app blocks the port.
- Your provider uses CGNAT, so incoming connections never reach your router. Use the check above.
- Your provider blocks the port. Some block 80, 445 or 25 on home lines.
- A second router or modem sits in front of yours and also needs a forwarding rule.
How this port checker works
Our server on Cloudflare opens a TCP connection to your public IP on each port. Open means the connection was accepted. Closed means your IP actively refused it. No response means nothing answered within 5 seconds, which usually means a router or firewall dropped it.
Only the IP address you're visiting from can be checked, so the tool can't be used to scan other people. It checks TCP only: browsers and servers on Cloudflare can't test UDP ports.
Questions
How do I check if a port is open?
Start the program that should answer, enter its port number above and click Check port. If the result is Open, the port is reachable from the internet. On your own computer, netstat -an shows which ports programs are listening on, but not whether the router lets connections in.
Why does my port show as closed after port forwarding?
Most often the program isn't running, the device's firewall blocks it, or the rule points to an old local IP. If everything looks right, check for CGNAT: when your router's WAN IP differs from your public IP, connections from the internet never reach your router.
Can I check UDP ports?
No. A UDP port doesn't confirm anything when it receives a packet, so it can only be tested with a program that answers on both sides. This checker tests TCP. Many games use both, so a forwarded TCP port is a good sign the UDP rule works too.
Is it safe to have open ports?
An open port is only as safe as the program behind it. Keep that program up to date, use strong passwords, and close ports you no longer use. Never expose Remote Desktop, SMB or a camera without a password; a VPN into your home network is safer.
Can I check a port on a different IP address?
No. Like CanYouSeeMe, this tool only checks the IP address you're visiting from, so nobody can use it to scan someone else's network. To check a server, open this page from that server's network.
Guides
- What is an IP address?
An IP address is the number that tells the internet where to send data meant for you. Here's what it looks like, the different kinds, and what yours says about you.
- How to find your IP address
Your public IP takes one click to find. Your private IP depends on the device. Here are the exact steps for each.
- IPv4 vs IPv6: what's the difference?
IPv6 replaces IPv4 because the world ran out of addresses. Here's how the two compare, how to tell which you're using, and why IPv6 matters if you use a VPN.
- What is a DNS leak and how do you fix it?
Even with a VPN on, your device may still ask your internet provider for every website you visit. That's a DNS leak. Here's how to spot one and stop it.