Checks the availability of one or more image layers that are within a repository in a public registry. When an image is pushed to a repository, each image layer is checked to verify if it has been uploaded before. If it has been uploaded, then the image layer is skipped.

This operation is used by the Amazon ECR proxy and is not generally used by customers for pulling and pushing images. In most cases, you should use the docker CLI to pull, tag, and push images.