Port 443 is the busiest port on the internet: by most measurements, the large majority of web page loads now use HTTPS. Because firewalls nearly always allow it, many non-web tools (VPNs such as OpenVPN TCP, SSH-over-TLS tunnels, video calls) also fall back to 443. On a Mac, outgoing connections to 443 are normal; what matters is which app makes them and to which domain.
Facts
- Port
- 443
- Protocols
- TCP, UDP
- Service
- HTTPS
What uses port 443
HTTPS: web browsing, APIs, app backends and most cloud services. TCP 443 carries HTTP/1.1 and HTTP/2 over TLS; UDP 443 carries HTTP/3 over QUIC. VPNs and other tools also use 443 because firewalls almost always allow it.
On a Mac
Your Mac connects out to port 443 constantly: browsers, App Store, iCloud, updates. Nothing on a Mac listens on 443 unless you run a local web server (for example a development proxy). Seeing hundreds of outgoing 443 connections is normal.
sudo lsof -nP -iTCP:443Security
Traffic is encrypted with TLS, so networks see the server name and amount of data, not the content. Exposing 443 on your own server is standard; keep the software patched.
Frequently asked questions
Is port 443 TCP or UDP?
Both. TCP 443 carries HTTPS over HTTP/1.1 and HTTP/2. UDP 443 carries HTTP/3, which runs over QUIC. Browsers use UDP when the server supports it.
Is it safe to have port 443 open?
Outgoing 443 is how you browse; it must be open. Inbound 443 is only open if you run a web server, and then it's safe as long as the server software is kept up to date.
Why do so many apps use port 443?
Firewalls almost always allow it, and TLS gives encryption for free. That makes 443 the most reliable port for any app that needs to reach the internet.