What is Port 443 used for?

Secure web. The protocol or service commonly associated with this port is HTTPS.

Role and operation

For HTTP/1.1 and HTTP/2, a client normally opens a TCP connection to port 443 and negotiates TLS before exchanging encrypted HTTP requests. The certificate presented by the server lets the client validate the service identity. HTTP/3 uses QUIC and can use UDP

Transport protocol

TCP

Security precautions

Keep TLS versions, cipher configuration, and certificates up to date. Restrict published services, patch web-application vulnerabilities, and protect certificate private keys.

Should this port be opened in the firewall?

For a public web service, TCP 443 can be published to the intended server or reverse proxy. For an internal application, restrict permitted sources and interfaces. Opening the port does not replace application-level and TLS security controls.

How can this port be checked?

On Windows, use Test-NetConnection SERVER -Port 443. You can also test HTTP/TLS with curl -I https://SERVER/ or inspect the certificate with an appropriate TLS tool.

Port 443 is conventionally associated with HTTPS. HTTP/3 can also use UDP 443 through QUIC.