You ran a port check and everything came back closed. Or the one port you cared about “failed” the test. Before you start changing router settings, take a breath. A failed port check is usually not a problem. Most of the time it means your firewall is doing exactly what you bought it for.
We have answered this question for over twenty years, and the answer has not changed: for a typical home computer, every port should report closed. That is a passing grade, not a failure.
What the three results actually mean
A port check sends a small request to your public address on a specific port and watches what comes back. There are only three outcomes.
Open means something on your network answered. A program is listening on that port and accepting connections from the internet. That should only be true if you set it up on purpose, for a game server, a camera system, remote access, or something else you recognize. If a port is open and you cannot name the program behind it, look the port up in our port database and find out what normally lives there.
Closed means your equipment replied, “nothing is listening here.” The door was knocked on and nobody answered because nobody is home. For everyday browsing, email, and streaming, this is what you want.
No reply at all is often labeled stealth or filtered. Your firewall dropped the request without answering. To an outside scanner your address looks like an empty lot instead of a locked door. Also fine.
One caution about UDP. TCP checks are reliable because TCP does a handshake. UDP has no handshake, so a UDP check that gets silence has to guess, and a timeout can look like closed or filtered when the truth is neither. Treat UDP results as a hint, not a verdict.
But I can browse the web, so port 80 must be open, right?
No, and this trips up almost everyone. When you load a website, your computer connects out to port 80 or 443 on the web server. The open port is on their end, not yours. Your side uses a temporary outbound connection, and your router lets replies back in automatically. You can have every inbound port slammed shut and browse all day. If that distinction is on your mind because a test said port 80 is closed, we cover it in detail in how to check if port 80 is open.
When closed is not what you wanted
Sometimes you need a port open, for a game, a camera, a server, and the check keeps saying closed. Work down this list in order, because each item depends on the one before it.
- Nothing is listening. A port only shows open when a program answers. Start the program or service first, then test. On Windows you can confirm locally with
netstat -anoin a command prompt, orTest-NetConnection -ComputerName localhost -Port 80in PowerShell. - The firewall on the computer is blocking inbound. Windows Defender Firewall and most security suites block unsolicited inbound connections by default. You need an inbound rule for the program or port. A reader named Caroline once lost FTP overnight because her host required a whole range of passive ports her firewall had never been told about. The firewall was not broken. It was just never asked.
- The router is not forwarding. Your router has to know which computer on your network gets traffic for that port. Without a forwarding rule, requests from the internet stop at the router. We walk through the common mistakes in port forwarding test not working.
- You tested from inside your own network. Many home routers cannot loop a request back around to their own public address. The check fails from your desk while working fine from the outside world. Test from a phone on cellular data instead of your Wi-Fi.
- A VPN is changing your address. With a VPN on, a port checker tests the VPN company’s server, not your house. Check what your public IP is first, and make sure it is the address you think you are testing.
- Your ISP blocks it or you never had a public address. Many providers block well-known ports like 25, and some block 80 on home plans. Others put whole neighborhoods behind carrier-grade NAT, where the address on your router is not reachable from the internet at all. No forwarding rule can fix that one; it takes a call to your provider.
Why check ports at all if I have a firewall?
Fair question, and a garage door answers it. The door closes and locks, so why ever check it? Because one day the remote code gets reused, or the door quietly stops latching, and you find out the hard way. A firewall is software and hardware, and both change. An update, a new program, a helpful “allow” click six months ago, a UPnP request from some gadget, any of these can open a hole you never hear about.
A port check is how you verify instead of assume. It also confirms the ports you opened on purpose, and only those, are actually reachable.
Running a check that means something
Decide what you expect before you test. Know which ports should be open (usually none) and look up any port you are unsure about. Check locally first so you know the program is listening, then check from outside on a different connection. And test again after any change, because a fix you did not verify is a guess.
For a walkthrough of what your connection exposes right now, start at our firewall test page.