Enter a host and port, or pick a preset.
Test a single port, a comma-separated list, or a range. Results show open, closed, or filtered for each port.
Only public hosts are supported. Private IPs (192.168.x.x, 10.x.x.x) cannot be tested.
Accepts a single port, comma-separated list, or a range like 8000-8010.
Three fields, one click.
No manual required — here's the entire flow.
Enter a host
Type a domain name like example.com or a public IP address like 8.8.8.8 into the host field.
Pick ports
Enter a single port (80), a list (80,443,22), or a range (8000-8010). Or tap one of the common presets.
Hit check
Press the Check button or hit Enter. Each port is tested in parallel from your browser.
Read the results
Each port shows open, closed, or filtered. Copy the plain-text summary if needed.
Clear status for every port.
No ambiguity — each port is tested and labelled.
Open
A service is listening and the port is reachable from the public internet. Good for web servers, APIs, and game servers.
Closed
The host is reachable, but nothing is listening on that port. The service may be stopped or not installed.
Filtered
A firewall, NAT rule, or cloud security group is silently dropping traffic. The host may be online, but that port is blocked.
Questions people actually ask.
The short answers — with the long ones one tap away.
What does a port checker do?+
A port checker attempts to connect to a specific TCP port on a target host and reports whether the port is open (accepting connections), closed (reachable but nothing listening), or filtered (blocked by a firewall or unreachable).
Can I check multiple ports at once?+
Yes. You can enter a single port like 80, a comma-separated list like 80,443,22, or a range like 8000-8010, and the tool will test each one.
What does 'filtered' mean?+
Filtered usually means a firewall, NAT rule, or cloud security group is silently dropping packets to that port. The host may be online, but that port is not reachable from the public internet.
Does this tool work on internal/private IP addresses?+
No. This tool runs in your browser and can only test hosts that are reachable from the public internet. Private addresses like 192.168.x.x, 10.x.x.x, or 127.0.0.1 cannot be tested.
Is it legal to check ports on a host I don't own?+
Only scan hosts you own or have explicit permission to test. Unauthorised port scanning may violate computer-misuse laws in your country. This tool is intended for checking your own servers, firewalls, and port-forwarding rules.
Is the tool free, and are my scans stored?+
Yes, it's completely free with no account or sign-up. Nothing you enter or scan is logged or stored by StudyWithSTEM.