If the container you’re hosting has a http web service on say port 8080, then you’d want to curl something at http://localhost:8080/. The particular URL/path you hit will depend on the app. If the app is particularly cloud-y, it might even have a specific endpoint for health checking by a container platform. If you share the name of the app I might be able to point you in the right direction.

Wat? Why are people health checking their containers by curl’ing example.com and not the service actually running in the container? Did they not understand that they’re supposed to change the curl URL to point at their actual service?