media-types.md

OCI Image Media Types

The following media types identify the formats described here and their referenced resources:

• application/vnd.oci.descriptor.v1+json: Content Descriptor
• application/vnd.oci.layout.header.v1+json: OCI Layout
• application/vnd.oci.image.index.v1+json: Image Index
• application/vnd.oci.image.manifest.v1+json: Image manifest
• application/vnd.oci.image.config.v1+json: Image config
• application/vnd.oci.image.layer.v1.tar: "Layer", as a tar archive
• application/vnd.oci.image.layer.v1.tar+gzip: "Layer", as a tar archive compressed with gzip
• application/vnd.oci.image.layer.nondistributable.v1.tar: "Layer", as a tar archive with distribution restrictions
• application/vnd.oci.image.layer.nondistributable.v1.tar+gzip: "Layer", as a tar archive with distribution restrictions compressed with gzip

Media Type Conflicts

Blob retrieval methods MAY return media type metadata. For example, a HTTP response might return a manifest with the Content-Type header set to application/vnd.oci.image.manifest.v1+json. Implementations MAY also have expectations for the blob's media type and digest (e.g. from a descriptor referencing the blob).

• Implementations that do not have an expected media type for the blob SHOULD respect the returned media type.
• Implementations that have an expected media type which matches the returned media type SHOULD respect the matched media type.
• Implementations that have an expected media type which does not match the returned media type SHOULD:
  • Respect the expected media type if the blob matches the expected digest. Implementations MAY warn about the media type mismatch.
  • Return an error if the blob does not match the expected digest (as recommended for descriptors).
  • Return an error if they do not have an expected digest.

Compatibility Matrix

The OCI Image Specification strives to be backwards and forwards compatible when possible. Breaking compatibility with existing systems creates a burden on users whether they are build systems, distribution systems, container engines, etc. This section shows where the OCI Image Specification is compatible with formats external to the OCI Image and different versions of this specification.

application/vnd.oci.image.index.v1+json

Similar/related schema

• application/vnd.docker.distribution.manifest.list.v2+json - mediaType is different

application/vnd.oci.image.manifest.v1+json

Similar/related schema

• application/vnd.docker.distribution.manifest.v2+json

application/vnd.oci.image.layer.v1.tar+gzip

Interchangeable and fully compatible mime-types

• application/vnd.docker.image.rootfs.diff.tar.gzip

application/vnd.oci.image.config.v1+json

Similar/related schema

• application/vnd.docker.container.image.v1+json

Relations

The following figure shows how the above media types reference each other:

Descriptors are used for all references. The image-index being a "fat manifest" references a list of image manifests per target platform. An image manifest references exactly one target configuration and possibly many layers.