In many situations, organizations will not want to place their applications and/or intellectual property in public repositories. For those cases, a private registry solution is helpful in securely integrating deployments end to end.

Google Cloud offers the Google Container Registry at https://cloud.google.com/container-registry/.

Docker has its own trusted registry offering at https://www.docker.com/docker-trusted-registry.

Quay also provides secure private registries, vulnerability scanning, and comes from the CoreOS team, and can be found at https://quay.io/.