8443 HTTPS-alternate TCP
Reference for TCP port 8443, commonly associated with HTTPS-alternate.
What it's for
Port 8443 is the most common alternate port for HTTPS, playing the same role for encrypted traffic that 8080 plays for plain HTTP — used when 443 is unavailable, reserved, or deliberately kept separate. It shows up frequently for admin panels, secondary services, and application servers (Tomcat's classic default HTTPS port) running alongside a site's main HTTPS endpoint on 443.
Protocol basics
Functionally, 8443 carries identical HTTPS/TLS semantics to port 443 — the same certificate validation, encryption, and HTTP-over-TLS behavior — just on a non-default port that must be explicitly specified in a URL (https://host:8443). Because browsers give no special implicit treatment to 8443 the way they do to 443, and because it still requires the exact same certificate and TLS configuration diligence, there's no meaningful security trade-off in using it — it's purely a matter of which port a given service happens to bind.