OCI

OCI (Open Container Initiative) is an open governance project, hosted under the Linux Foundation, that maintains vendor-neutral specifications for containers. It grew out of Docker’s early formats and exists so that a container image built with one tool runs consistently on any runtime or registry that conforms to the specs. In practice OCI is the reason “container” stopped meaning “Docker” and became a portable, interoperable unit of software.

• Image Specification - Defines the on-disk format of a container image — layers, configuration, and manifest — independent of any single vendor.
• Runtime Specification - Describes how to unpack and execute a container so runtimes like runc, containerd, and CRI-O behave the same way.
• Distribution Specification - Standardizes the registry API for pushing and pulling images, which is why OCI registries now store more than just container images.
• Vendor neutrality - Governed in the open so no single company controls how containers are built, shipped, or run.

For API work, OCI matters because it standardizes the units APIs and microservices ship in. Almost every modern API deployment — Kubernetes, serverless container platforms, CI/CD pipelines — assumes OCI-compliant images, so the packaging of an API is now as much a standard as the interface itself. The OCI distribution spec has also been repurposed as a general artifact store, meaning OpenAPI definitions, Helm charts, and other API governance artifacts increasingly travel through the same registries as the containers they describe. Containers, as I wrote years ago, do for APIs what APIs did for companies — and OCI is what keeps that portable.