Encrypted web traffic. TCP carries HTTP/1.1 and HTTP/2 over TLS; UDP 443 carries HTTP/3 over QUIC.
A browser sends an HTTP request to port 443 and the HTTPS server sends the page back. Everything is encrypted: someone on the path only sees unreadable bytes.
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| https | 443 | TCP, UDP, SCTP | http protocol over TLS/SSL | RFC 9110 | 2021-10-01 |
// source: IANA service name and port number registry
Linux
sudo ss -ltnup 'sport = :443' # process listening on 443
sudo lsof -nP -i :443macOS
sudo lsof -nP -i :443
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 443 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 443 netstat -ano | findstr :443
From another machine
nmap -p 443 -sV <host> sudo nmap -sU -p 443 <host> nc -zv <host> 443
Block it in the firewall
sudo ufw deny 443/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 443" -Direction Inbound -LocalPort 443 -Protocol TCP -Action Block # Windows
Encrypted web traffic. TCP carries HTTP/1.1 and HTTP/2 over TLS; UDP 443 carries HTTP/3 over QUIC.
Port 443 is registered for TCP and UDP and SCTP. In practice the service mostly uses TCP and UDP.
It is rated 2/10 (low) when exposed to the Internet. The port itself is safe; the exposure is the web application behind it (injection, authentication flaws, outdated CMS). Allow TLS 1.2 and 1.3 only and enable HSTS.
On Linux run "ss -ltnup 'sport = :443'", on macOS "lsof -nP -i :443", and on Windows "netstat -ano | findstr :443" to see the local process. From another machine, "nmap -p 443 <host>" shows whether it is reachable.