How to use the Port Checker
- Enter a domain or public IP address.
- Enter the ports to test, or click a preset (web, mail, databases, remote access).
- Click Check ports. Each port gets a TCP connection attempt with a 3-second timeout.
- Read the result: open accepts connections, closed actively refuses, filtered doesn’t answer (usually a firewall).
Open, closed or filtered?
| Status | Meaning |
|---|---|
| Open | A service is listening and accepted the connection. |
| Closed | The host is reachable but refused the connection — nothing listens on that port. |
| Filtered | No answer within 3 seconds — a firewall silently drops the traffic, or the host is offline. |
Common ports
| Port | Service | Should usually be public? |
|---|---|---|
| 80 / 443 | HTTP / HTTPS | Yes, for websites |
| 25, 465, 587 | SMTP (mail transfer & submission) | On mail servers |
| 993 / 995 | IMAPS / POP3S | On mail servers |
| 22 | SSH | Only if needed — restrict by IP or key-only login |
| 3306, 5432, 1433, 27017, 6379 | MySQL, PostgreSQL, MS SQL, MongoDB, Redis | Almost never — keep databases private |
| 3389, 5900 | RDP, VNC | No — a frequent attack target |
Use it responsibly
Check servers you own or administer — for example to verify a firewall rule, port forwarding on a router, or that a database isn’t exposed. The tool tests a short list of ports only and is rate-limited; it’s not a full scanner. For web-specific checks see the SSL Checker, Security Headers Checker and Ping Test.
Tools that pair well with the Port Checker
- SPF, DKIM & DMARC Checker — Find out why emails land in spam.
- Website Down Checker — Find out in seconds whether a website is down for everyone or just for you — with status code, response time and troubleshooting tips.
- DNS Lookup — Query all common DNS record types for a domain in one go, with TTLs, sorted MX records and an SPF/DMARC email-authentication summary.
- WHOIS Lookup — Enter a domain to see its registrar, creation and expiry dates, domain age, status codes, nameservers and DNSSEC — or an IP address to find the network and organisation that owns it.
Frequently asked questions
How do I check if a port is open?
Enter the host and the port numbers, then click Check ports. “Open” means a service accepted the connection from the internet.
Why is my port shown as filtered?
No response arrived within 3 seconds. A firewall (on the server, your hosting provider or router) is probably dropping the traffic, or the device is offline.
Can I test port forwarding on my home router?
Yes — enter your public IP (see What Is My IP) and the forwarded port while the service is running. Private addresses like 192.168.x.x can’t be tested from the internet.
Why is port 25 blocked?
Many ISPs and cloud providers block outgoing or incoming port 25 to fight spam. Mail clients should use 587 (submission) or 465 instead.