CRI-O is an implementation of the Kubernetes CRI (Container Runtime Interface) to enable using OCI (Open Container Initiative) compatible runtimes. It is a lightweight alternative to using Docker as the runtime for kubernetes. It allows Kubernetes to use any OCI-compliant runtime as the container runtime for running pods. Today it supports runc and Clear Containers as the container runtimes but any OCI-conformant runtime can be plugged in principle. CRI-O supports OCI container images and can pull from any container registry. It is a lightweight alternative to using Docker, Moby or rkt as the runtime for Kubernetes.