Port 443: HTTPS (Hypertext Transfer Protocol Secure)

What is port 443 used for?

Port 443 is HTTPS: HTTP carried inside a TLS connection. It is the port behind every https:// address and, today, behind most web traffic, APIs and cloud services.

TLS on 443 gives three things: the traffic is encrypted, it cannot be altered unnoticed, and the server proves its name with a certificate. Because 443 is open outbound almost everywhere, many other services run over it, including VPNs, DNS over HTTPS and remote access gateways, and so does malware command traffic. That is why organizations inspect or filter HTTPS instead of trusting the port. A certificate warning on 443 means the name, the date or the issuer does not check out, and should not be clicked through.

Is port 443 TCP or UDP?

Both. HTTPS over HTTP/1.1 and HTTP/2 uses TCP 443. HTTP/3 runs over QUIC, which uses UDP 443. A firewall that allows only TCP 443 still works, because clients fall back from HTTP/3 to the TCP-based versions.

Does port 443 mean a site is safe?

It means the connection is encrypted and the server holds a valid certificate for that name. It says nothing about who runs the site: phishing pages use HTTPS too. The padlock protects the transport, not the content.

Port 443 vs port 80: what is the difference?

Port 80 is HTTP in clear text. Port 443 is the same HTTP inside TLS, encrypted and with the server authenticated by a certificate. Sites keep 80 open only to redirect visitors to 443. Port 80 explained

Which CompTIA exams list port 443?

CompTIA lists port 443 by number in both the Network+ and the A+ Core 1 objectives.

• Network+ N10-009: objective 1.4 (Networking Concepts), listed as “Hypertext Transfer Protocol Secure (HTTPS), 443”.
• A+ Core 1 220-1201: objective 2.1 (Networking), listed as “443, Hypertext Transfer Protocol Secure (HTTPS)”.

The quoted text is how the objectives document lists the port. The exam puts the port in a scenario, such as a firewall rule or a failed connection; it does not only ask for the number.

Check yourself: a practice question

Written by CertSprint for this page. It is not taken from any exam.