Port 443 (HTTPS)
Port 443 is HTTPS, the encrypted web. Every address that starts with https:// connects here unless another port is written in the URL; many VPNs and APIs also use 443 because firewalls rarely block it.
- Service
- HTTPS
- Protocol
- TCP and UDPTCP for HTTP/1.1 and HTTP/2. HTTP/3 runs over QUIC on UDP 443, so a modern server listens on both.
- IANA registry
- Officially assigned: https (http protocol over TLS/SSL), TCP/UDP
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 443?
Port 443 is meant to be open on a web server. What matters is the certificate (valid, not expired, matching the name), a current TLS version and up-to-date server software. Check the certificate of any site with our SSL checker.
Sources
“Port 443 is already in use”: how to fix it
The error means another program is already listening on port 443. 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 :443taskkill /PID <PID> /FmacOS
lsof -nP -iTCP:443 -sTCP:LISTENkill <PID>Linux
sudo ss -ltnp | grep :443sudo lsof -i :443sudo kill <PID>Replace <PID> with the number from the last column (Windows) or the PID column (macOS, Linux).
Port 443 vs 80
Port 80 is HTTP without encryption; 443 is HTTPS with TLS. A modern site serves everything on 443 and keeps 80 only to redirect visitors there.
Port 80 (HTTP)Port 443 vs 8443
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 8443 (HTTPS alternate)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 443 used for?
Port 443 is HTTPS, the encrypted web. Every address that starts with https:// connects here unless another port is written in the URL; many VPNs and APIs also use 443 because firewalls rarely block it.
Is port 443 TCP or UDP?
TCP for HTTP/1.1 and HTTP/2. HTTP/3 runs over QUIC on UDP 443, so a modern server listens on both.
Is it safe to open port 443?
Port 443 is meant to be open on a web server. What matters is the certificate (valid, not expired, matching the name), a current TLS version and up-to-date server software. Check the certificate of any site with our SSL checker.
How do I free port 443 if it is already in use?
Find the process: on Windows run netstat -ano | findstr :443 and stop it with taskkill /PID <pid> /F; on macOS or Linux run lsof -i :443 and stop it with kill <pid>.