Port 8443 (HTTPS alternate)
Port 8443 is the conventional alternative HTTPS port: Apache Tomcat uses it for its TLS connector, and many admin interfaces and appliances serve their web console on 8443. IANA registers it for PCsync HTTPS.
- Service
- HTTPS alternate
- Protocol
- TCP
- IANA registry
- Assigned to a different service: pcsync-https (PCsync HTTPS), TCP/UDP. The use described here is not registered.
- Commonly used by
Check if a port is open on your IP
We only check the address you are visiting from, one TCP port at a time. You cannot enter someone else’s address: this is not a port scanner.
Is it safe to open port 8443?
Services on 8443 are often management consoles. Restrict them to trusted addresses and keep their certificates valid; the certificate of your main domain can be checked with our SSL checker.
“Port 8443 is already in use”: how to fix it
The error means another program is already listening on port 8443. Find its process ID (PID), then stop that program or start yours on a different port.
Windows (Command Prompt or PowerShell as administrator)
netstat -ano | findstr :8443taskkill /PID <PID> /FmacOS
lsof -nP -iTCP:8443 -sTCP:LISTENkill <PID>Linux
sudo ss -ltnp | grep :8443sudo lsof -i :8443sudo kill <PID>Replace <PID> with the number from the last column (Windows) or the PID column (macOS, Linux).
Port 8443 vs 443
443 is the standard HTTPS port that browsers use without a number in the address; 8443 is an alternative for a second HTTPS service on the same machine, typically an admin console or Tomcat. Visitors must type :8443, so public sites stay on 443.
Port 443 (HTTPS)Why a port can look closed when your server is running
Most home networks sit behind a router doing NAT: the router owns the public address, and your computer has a private one such as 192.168.1.10. A connection from the internet reaches the router and stops there unless you add a port forwarding rule to your computer.
Many mobile and some home providers go further and use carrier-grade NAT (CGNAT): several customers share one public address, and your router itself gets an address from 100.64.0.0/10. Then no rule on your side can open a port; ask the provider for a public IP or use a tunnel or VPN service.
Even with forwarding in place, the firewall on the computer (Windows Defender Firewall, ufw, firewalld) must allow the port, and the program must listen on all interfaces (0.0.0.0), not only on 127.0.0.1.
UDP cannot be checked this way: a UDP service usually stays silent to packets it does not understand, so “no answer” means nothing. This check uses TCP only.
Frequently asked questions
What is port 8443 used for?
Port 8443 is the conventional alternative HTTPS port: Apache Tomcat uses it for its TLS connector, and many admin interfaces and appliances serve their web console on 8443. IANA registers it for PCsync HTTPS.
Is port 8443 TCP or UDP?
Port 8443 uses TCP. This use is not registered with IANA.
Is it safe to open port 8443?
Services on 8443 are often management consoles. Restrict them to trusted addresses and keep their certificates valid; the certificate of your main domain can be checked with our SSL checker.
How do I free port 8443 if it is already in use?
Find the process: on Windows run netstat -ano | findstr :8443 and stop it with taskkill /PID <pid> /F; on macOS or Linux run lsof -i :8443 and stop it with kill <pid>.