An application has no public address and no public URL of its own. This is on purpose: nothing is exposed until you decide to expose it. Its pages show it as Private, reached through a Cloud Firewall, and the app's own Domains tab cannot publish it. You make an app public by putting a Cloud Firewall in front of it.
Why there is no domain on the app itself
Adding a domain directly to an application is not supported, and the platform will tell you so if you try. A domain, its certificate and its public address live on the Cloud Firewall, which is the one thing that holds a public address, so that is where routing is configured. One firewall can front several apps.
Publish an app in three steps
- Put the app on a private network. Connect the app and the firewall to the same private network.
- Create or reuse a Cloud Firewall on that network. See Create a Cloud Firewall.
- Add a route on the firewall's load balancer: a domain with HTTPS, and a backend that points at your application. When you add the backend, pick the app from the Application list and the firewall tracks its private address for you.
Point the domain's DNS at the firewall's public address, and the firewall issues a free HTTPS certificate once it resolves.
Just need outbound internet?
If the app does not need to be reachable from the internet but does need to make outbound calls (to an API, a package registry or an SMTP server), a Cloud Firewall with NAT on its network gives it egress with no public address and no inbound exposure.