the healthcheck URL should point to some HTTP API that the container makes available, so it should point to the container.

in place of localhost should be the container’s name, and port should be the port the container exposes as the web server. some services, like Jellyfin, have a specific webpage path for this purpose: jellyfin.org/docs/general/…/monitoring/

and others, like gitea, hide the fact well that they have a health check endpoint, because its nkt mentioned in documentation: github.com/go-gitea/gitea/pull/18465

but check if docker’s way of doing healthchecks produces a lot of spam in the system log,in which case you could choose to just disable health checking, because it would push out useful logs