Port 443 — HTTPS

TCP well-known

What runs on port 443

Encrypted web traffic. The default for essentially all modern web services, and the transport for HTTP/2 and HTTP/3.

Security considerations

HTTP/3 runs over QUIC on UDP 443 — if you firewall only TCP, HTTP/3 silently fails and clients fall back.

Checking whether something is listening

# Linux / macOS — what is bound to the port
sudo lsof -i :443
sudo ss -lntp | grep :443

# Windows
netstat -ano | findstr :443
Get-NetTCPConnection -LocalPort 443

# is it reachable from outside?
nc -zv example.com 443
curl -v telnet://example.com:443

Freeing the port

# find the process, then stop it
sudo lsof -ti :443 | xargs kill        # Linux / macOS
netstat -ano | findstr :443            # note the PID, then:
taskkill /PID <pid> /F                    # Windows

Should this port be open to the internet?

Yes — that is what it is for. Make sure whatever is listening is something you intend to expose, and that TLS is configured properly.

Quick reference

Frequently asked questions

Other common ports

• Port 20 — FTP data
• Port 21 — FTP control
• Port 22 — SSH / SFTP
• Port 23 — Telnet
• Port 25 — SMTP
• Port 53 — DNS
• Port 67 — DHCP server
• Port 68 — DHCP client
• Port 69 — TFTP
• Port 80 — HTTP
• Port 110 — POP3
• Port 123 — NTP
• Port 143 — IMAP
• Port 161 — SNMP
• Port 389 — LDAP
• Port 445 — SMB
• Port 465 — SMTPS
• Port 514 — Syslog

All port numbers