Port 443 is assigned to HTTPS, the encrypted version of HTTP.
HTTPS combines the Hypertext Transfer Protocol with a cryptographic security layer, traditionally TLS. When a browser connects to an HTTPS website, it normally uses TCP port 443 as the destination port, although services can be configured to use other ports. The server presents a digital certificate, and the connection negotiates encryption and authentication before web data is exchanged.
HTTP conventionally uses port 80, which is why port 443 is a useful distinction when examining web traffic or configuring firewalls. Port numbers identify service endpoints; they do not themselves provide encryption. A service listening on port 443 is not automatically secure unless it correctly implements TLS and uses a valid configuration.
HTTPS protects data in transit from ordinary interception and helps a browser verify the intended website through certificate validation. It does not guarantee that a site is honest, that the computer is malware-free, or that information is safe after the website receives it. HTTPS was standardized through the development of HTTP over TLS and is now the normal basis for secure web browsing.