Developer Tools

Online Port Checker

Check if a TCP port is open on any server or IP address. Test ports like 80, 443, 22, 3306, and more. Instant results, no signup.

Try:
Ports:

Enter a host and port to check if it is open

Or use Common Ports Scan to check multiple ports at once

Free Online Port Checker — Check If a Port Is Open

What Is a Port Checker?

A port checker tests whether a specific TCP port is open and reachable on a remote server or IP address. Ports are numbered endpoints (1 to 65535) that allow different services to run on the same server — port 80 for HTTP, port 443 for HTTPS, port 22 for SSH, port 3306 for MySQL, and so on. Our free online port checker connects from our external server to give you a true outside-in view of whether your port is accessible from the internet.

How to Use This Port Checker

Enter the hostname or IP address of the server you want to check (or click "Use My IP"). Enter the port number or click a common port preset (Web 80/443, SSH 22, MySQL 3306, etc.). Click "Check Port" and view the result — open (green), closed (red), or filtered (yellow). For open ports, the connection response time is also displayed.

Key Features

  • Clear results — color-coded open (green), closed (red), and filtered (yellow) status
  • Common port presets — one-click buttons for HTTP, HTTPS, SSH, FTP, SMTP, MySQL, PostgreSQL, MongoDB, and more
  • Response time — millisecond connection latency for open ports
  • Use My IP — auto-detect your public IP address for self-testing
  • All ports supported — test any TCP port from 1 to 65535
  • External perspective — checks from our server, not your local network

Understanding Port States

When you check a port, three outcomes are possible. Open means the server accepted the TCP connection — a service is actively listening on that port and clients can connect. Closed means the server responded with a TCP RST (reset) packet — the host is reachable but no service is listening on that port. Filtered means no response was received within the timeout period — this typically indicates a firewall is silently dropping packets, making it impossible to determine whether a service is running behind it.

Common Use Cases

  • Firewall verification — confirming that firewall rules are correctly allowing traffic on specific ports
  • Deployment checks — verifying that a service is listening after deploying a new application
  • Troubleshooting — diagnosing why clients cannot connect to a server
  • ISP blocking detection — checking whether your ISP blocks specific ports like 25 (SMTP) or 80 (HTTP)
  • Security auditing — verifying that unused ports are properly closed

Tips and Best Practices

If a port shows as filtered, check each network layer from outside in: cloud security groups, network firewalls, host-based firewalls (iptables, Windows Firewall), and NAT/port forwarding rules. Remember that this tool checks TCP ports only — UDP services require different testing methods. When testing your own server behind NAT, ensure port forwarding is configured on your router. A closed port is actually a good sign for security — it means the host is reachable and actively refusing connections on that port, rather than silently dropping packets. For production servers, only the ports needed by running services should be open.

Frequently Asked Questions