Harbor v2.0 now supports OCI images and OCI image indexes (https://github.com/opencontainers/image-spec/blob/master/image-index.md). An OCI image index (or OCI index) is a higher level manifest which points to a list of image manifests, ideal for one or more platforms. Both the index itself and the images referenced within are referred to as artifacts in Harbor parlance. An OCI index could hold another OCI index and so on and so forth. For any artifact referenced by an OCI index, the referenced artifact is known as the child artifact and the OCI index referencing the artifact is known as the parent artifact. We can also say that the child artifact belongs to the parent artifact or is a part of the parent artifact.
When an artifact is not referenced by any OCI index, you can delete the artifact freely which will delete its manifest and all associated tags.
When an artifact is referenced by an OCI index, you cannot delete it. In order to delete this artifact, you must first delete all OCI indexes referencing this artifact first, remembering that an artifact can be referenced by multiple parents artifacts pushed onto Harbor by different users. So when deleting an OCI index holding 9 children artifacts not referenced by any other index and 1 child artifact referenced by another index, only 9 out of 10 children artifacts will be deleted.
To delete any artifact in the Harbor interface, click on the artifact and select ‘Delete’ and confirm.