What is an open port checker?

An open port checker tests whether a TCP port on a public host accepts connections from the internet. Enter a domain or IP, choose ports, and the table shows Open or Closed/Filtered plus latency for each open port.

How do I check open ports on my own computer?

Use your operating system to list listening ports. On Windows run netstat -an, on Linux or Ubuntu run ss -tuln, and on Mac run lsof -iTCP -sTCP:LISTEN -n -P. Then test your public IP here to see what the internet can reach.

Why does a port show Closed/Filtered when my service is running?

A running service can still be unreachable if a firewall, router or cloud security group blocks the port, or if the service listens only on localhost. Check those, then run Check Ports again to confirm the fix.

Can I check UDP ports or private IP addresses like 192.168.1.1?

No. The tool tests TCP ports only, and only on public hosts. Local, private and reserved ranges are blocked, so test those from inside your own network with local commands such as netstat or ss.

How many ports can I test at once with the open port checker?

You can test up to 25 ports per run, combining the ticked service ports with up to 10 custom ports. Custom ports must be numbers from 1 to 65535, separated by commas, such as 8080, 8443, 25565.

Is the open port checker free, and does it need a sign-in?

Yes, the tool is free and needs no sign-in. Type a host, pick ports and click Check Ports. Use it only on hosts you own or are authorized to test.

Open Port Checker: Test TCP Ports Online Free

An open port checker tests whether a TCP port on a public server accepts connections from the internet. Enter a domain or IP address, tick common service ports or add your own, and the tool returns each port's status and connection latency. It helps site owners, admins and gamers confirm that a service is reachable.

What Is an Open Port in Networking?

An open port is a numbered network endpoint, from 1 to 65535, where a program is listening and accepts incoming connections. Each service has a conventional number: web traffic uses 80 (HTTP) and 443 (HTTPS), remote login uses 22 (SSH), and outgoing email uses 25 (SMTP).

A TCP port test works by attempting a connection. If the handshake completes, the port is open. If the host refuses the attempt, the port is closed. If a firewall silently drops the attempt, the port is filtered. From the outside, closed and filtered ports look almost the same, so this tool reports both as Closed/Filtered.

In cyber security, every open port is a possible entry point because it exposes a running service. That is why administrators keep open only the ports a service genuinely needs and check them regularly.

How to Use the Open Port Checker

You can run a full check in under a minute by following these steps.

Type a domain or public IP address into Host or domain, for example example.com or 93.184.216.34. If you paste a full URL, the tool uses only the host name.
Under Ports to check, tick the services you want to test. Ports 80, 443 and 22 are selected by default. The list also includes 21 (FTP), 25 (SMTP), 53 (DNS), 110 (POP3), 143 (IMAP), 465 (SMTPS), 587 (Submission), 993 (IMAPS), 995 (POP3S), 3306 (MySQL), 5432 (PostgreSQL), 6379 (Redis) and 27017 (MongoDB).
If your service uses another port, add it under Custom ports (comma-separated, max 10), for example 8080, 8443, 9000. Valid numbers run from 1 to 65535.
Click Check Ports. You can test up to 25 ports in one run, counting ticked and custom ports together.
Read the Results for table. The address in parentheses is the IP the tool actually tested. The columns show Port, Service, Status and Latency.
Change your firewall, router or service settings if needed, then run the check again to confirm the fix.

Worked Example: Checking a New Web Server

Say you just launched a site and want to confirm it is reachable. You enter your domain, leave 80, 443 and 22 ticked, and type 8080 in the custom ports box. A realistic result looks like this:

Port 80 (HTTP): Open, 24 ms
Port 443 (HTTPS): Open, 31 ms
Port 22 (SSH): Closed/Filtered
Port 8080: Closed/Filtered

Here is how to read it. Ports 80 and 443 are open, so visitors can reach the site over HTTP and HTTPS. Port 22 is closed or filtered, which is fine if you manage the server only from a trusted network or a VPN. Port 8080 is closed, which is expected if no app listens there. If you needed SSH from anywhere, you would now check the server firewall and the SSH service itself.

How Do You Read the Results?

Each row tells you whether a TCP connection to that port succeeded and how long it took. Use the table below to decide what to do next.

Result	Meaning	Next step
Open with a latency	A service accepted the connection	Confirm it is a port you intend to expose
Closed/Filtered	Refused, blocked or no answer	Check the service, firewall and port forwarding
Fewer rows than expected	The check ended early with partial results	Run again with fewer ports

What Does Latency Mean Here?

Latency is the time the connection took to complete, shown only for open ports. As a rough guide, a nearby host often answers in tens of milliseconds, while a host on another continent may take a few hundred. A single reading is a snapshot, so run it twice before drawing conclusions about speed.

Which Ports Should Be Open?

It depends on the job of the host. A typical website needs 80 and 443. A mail host may need 25, 465, 587 and 993. Database ports such as 3306 (MySQL), 5432 (PostgreSQL), 6379 (Redis) and 27017 (MongoDB) should normally not be reachable from the public internet. If one shows Open, restrict it to trusted IP addresses or a private network.

How to Check Open Ports on Windows, Linux and Mac

This page tests a host from the outside, while your own operating system can show what is listening locally. Use both views together.

Windows and Windows 11: open Command Prompt and run netstat -an. Look for lines marked LISTENING.
Linux and Ubuntu: run ss -tuln to list listening TCP and UDP sockets.
Mac: run lsof -iTCP -sTCP:LISTEN -n -P in Terminal.
Router: sign in to the admin page and look for the port forwarding or virtual server section.

Now compare. If a port is listening on your machine but shows Closed/Filtered here, something between the internet and the service is blocking it, usually a firewall rule or a missing port forward. To test a home connection, enter your public IP address, not the 192.168.x.x address your device shows.

Who Uses an Open Port Checker?

Anyone who needs to know whether a service can be reached from outside their own network benefits from this check. Common situations include:

Site owners confirming ports 80 and 443 respond before an SSL certificate is issued or a launch goes live.
Game hosts testing a custom port, such as 25565, the default for a Minecraft Java server.
Email administrators checking 25, 465, 587 and 993 after a mail server change.
Developers and DevOps teams making sure database ports are not exposed by mistake.
Support staff deciding quickly whether a complaint is a network block or an application bug.

Best Practices and Troubleshooting Tips

Most surprising results come from a handful of causes, and each has a quick fix.

The Port Shows Closed but the Service Is Running

Check these in order: whether the service is bound only to localhost (127.0.0.1) instead of all interfaces, whether the host firewall allows the port, whether a cloud security group or router forward is missing, and whether your provider blocks the port. Residential connections often block port 25, for example.

The Result Does Not Match Your Server

The tool tests the public IP the host name resolves to. If your domain sits behind a proxy or CDN, you are testing the proxy, which usually answers only on web ports. Review your records with a DNS lookup or an A record lookup, and check IPv6 with an AAAA record lookup. If you only have a URL and need its address, a domain to IP lookup gives you one.

You See a Public Address Error

Local, private and reserved ranges such as 192.168.1.1 or 10.0.0.5 are blocked. Test those hosts from inside the same network with the local commands above.

Some Rows Are Missing

Ports that do not answer make the check wait, and a long list can end early with partial results. Test fewer ports at a time, starting with the ones that matter most.

Other Good Habits

Test only hosts you own or are authorized to check.
Run the check again after every firewall or router change.
If a surprising IP comes back, an ASN lookup shows which network owns it.
Close any port you do not recognize, after confirming nothing depends on it.

Limitations and Accuracy Notes

This is a connectivity test for individual TCP ports, not a full security audit. It does not test UDP, so services that rely on UDP, such as many game servers and DNS queries, cannot be verified here. It also cannot tell a closed port from a filtered one, and it does not identify the software behind a port or look for vulnerabilities.

Each result reflects one moment and one network path. A host that blocks certain regions or rate-limits connections may look closed even though other users can reach it. Treat the result as strong evidence, then confirm with logs on the host.

Enter your host above, keep the default ports or add your own, and click Check Ports to see what is reachable right now. For more diagnostics, browse the network and IP tools.

Open Port Checker: Test TCP Ports Online Free