80
Unencrypted web traffic (HTTP)
HyperText Transfer Protocol
What is port 80?
HTTP on port 80 is the foundational protocol of the web. When you type a URL without https://, the browser connects on port 80. Today, port 80 is primarily used to issue 301 redirects to HTTPS (port 443) and to serve ACME HTTP-01 challenges for Let's Encrypt certificate issuance. All communication is unencrypted, so passwords and sensitive data are visible on the network. Production systems should always serve content over HTTPS.
Quick checks
$
nc -zv example.com 80
$
nmap -p 80 example.com
$
telnet example.com 80