Port 443 (TCP & UDP) — HTTPS & HTTP/3 (QUIC)
Port 443 carries TLS-encrypted web applications, REST/gRPC APIs, WebSockets over TCP/443, and modern HTTP/3 multiplexed streams over QUIC (UDP/443).
| Port Number | 443 |
|---|---|
| Transport Protocol | TCP & UDP |
| Primary Service | HTTPS & HTTP/3 (QUIC) |
| Standard / Specification | RFC 9110 / RFC 9000 |
| IANA Port Range | Well-Known System Port (0–1023) |
| Internet Exposure Risk | Standard public web ingress; harden TLS 1.2/1.3 ciphers and WAF policies. |
Firewall Architecture & Hardening Best Practices
Permit inbound TCP/443 on public CDNs, reverse proxies, and ingress controllers; also open inbound UDP/443 if enabling HTTP/3 QUIC for lower handshake latency on mobile networks.
Operational Troubleshooting Note
Inspect TLS certificate chains, ALPN negotiation, and expiration dates using openssl s_client -connect example.com:443 -servername example.com.
Quick CLI Connectivity & Firewall Reference
# Test TCP/443 reachability (Linux / macOS / PowerShell) nc -zv target.example.com 443 Test-NetConnection -ComputerName target.example.com -Port 443 # Inspect local UDP/443 socket binding on Linux ss -uapn | grep :443 # Allow restricted CIDR on Linux UFW firewall ufw allow from 10.0.0.0/8 to any port 443 proto any
Planning firewall allowlists or VPN overlays? Use our IPv4 CIDR Calculator, MTU & TCP MSS Calculator, or WireGuard AllowedIPs Generator.
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