443/TCPHTTPS
Web · Well-known port · OSI layer 7
Encrypted websites and APIs over TLS. HTTP/3 also uses UDP 443 (QUIC), so allow UDP as well.
IANA: officially registered as https
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Port 443: Check and open the HTTPS port
Port 443 is the default port for HTTPS: encrypted HTTP over TLS. Here you’ll find all the key details about the port and ready-to-use firewall commands to open it on your server.
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Firewall commands
Open port
sudo ufw allow 443/tcpNotes on ufw
For Ubuntu and Debian. ufw creates the rule for both IPv4 and IPv6. If ufw is disabled, allow SSH first (sudo ufw allow 22/tcp), then enable it with sudo ufw enable, or you'll lock yourself out.
On a ZAP-Hosting VPS with an active network firewall, you also need to allow the port in the Customer Panel.
Port 443 explained
What is port 443 used for?
Purpose
Most web traffic today uses port 443: websites, online stores, web apps and REST APIs. The browser first establishes a TLS connection and checks the server’s certificate before transmitting the HTTP data securely. HTTPS traditionally uses TCP. HTTP/3, however, runs over QUIC and uses UDP 443, so you should allow both protocols on modern web servers.
Origin and standard
HTTPS traces back to the SSL protocol developed by Netscape in the mid-1990s. HTTP over TLS is described in RFC 2818, and the current TLS version, 1.3, in RFC 8446. IANA lists port 443 as a Well-Known Port named “https”. HTTP/3 is standardized in RFC 9114 and builds on QUIC, described in RFC 9000.
Typical use
- Websites and online stores with a TLS certificate, for example from Let’s Encrypt
- REST APIs and webhooks that transfer data securely
- Reverse proxies such as nginx, Apache, Caddy or Traefik as a central entry point
- HTTP/3 over QUIC on UDP 443
- VPN and remote gateways that deliberately use 443 because the port is open almost everywhere
Security
Port 443 can be publicly accessible on a web server—that’s its purpose. What matters is the TLS configuration: allow only TLS 1.2 and TLS 1.3, and disable older versions such as SSL 3.0, TLS 1.0 and TLS 1.1. Renew certificates automatically so they don’t expire unnoticed. HSTS ensures browsers access your site only over HTTPS. A web application often runs behind port 443, so keep your web server, CMS and plugins up to date: most attacks target the application, not the port.
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View all well-known ports and the complete IANA list
Port list source: IANA Service Name and Transport Protocol Port Number Registry, as of October 22, 2026. iana.org
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FAQ
Frequently asked questions
Quick answers about port 443.
Traditional HTTPS uses TCP 443. HTTP/3 runs over QUIC and uses UDP 443. If your web server offers HTTP/3, allow both protocols; otherwise, browsers will automatically fall back to TCP.
With ufw, sudo ufw allow 443/tcp is enough. For HTTP/3, also run sudo ufw allow 443/udp. With firewalld, use sudo firewall-cmd --permanent --add-port=443/tcp, then reload the rules with sudo firewall-cmd --reload.
Port 80 carries unencrypted HTTP; port 443 carries HTTPS encrypted with TLS. Today, port 80 should only redirect to HTTPS. All content, logins and forms belong on port 443.
An open port only means that a service accepts connections. Common causes include an expired or incorrect certificate, an incorrect DNS record, or a web server without a matching virtual host for the domain. First use the port checker to see whether the port is accessible externally, then check your web server logs.
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