Port 443: HTTPS

What is port 443 used for?

Encrypted web traffic (HTTP over TLS). HTTP/3 uses UDP 443 as well.

Should port 443 be open?

Usually open to the internet. This port is meant to be reachable publicly on servers that offer the service. The one port every public website needs. If 443 is closed, check the firewall, the cloud security group and whether the web server is listening on all interfaces. Check the certificate with the SSL Checker.

See what is listening on port 443

# Linux
sudo ss -tlnp | grep ':443 '

# macOS
sudo lsof -nP -i TCP:443 -sTCP:LISTEN

# Windows (PowerShell)
Get-NetTCPConnection -LocalPort 443 -State Listen

Open or block port 443 in a firewall

# Ubuntu / Debian (ufw)
sudo ufw allow 443/tcp
sudo ufw deny 443/tcp

# Windows (PowerShell, as administrator)
New-NetFirewallRule -DisplayName "Port 443" -Direction Inbound -Protocol TCP -LocalPort 443 -Action Allow

On cloud servers, also open the port in the provider’s security group or network firewall. At home, a service behind a router needs a port-forwarding rule to the device’s local IP.

Test it from outside

A port can be open on the server but blocked upstream. The Port Checker connects from the internet, so it shows what the world sees. From your own machine, use nc -vz example.com 443 (macOS/Linux) or Test-NetConnection example.com -Port 443 (Windows).