# OCI Image Manifest Specification

There are three main goals of the Image Manifest Specification.
The first goal is content-addressable images, by supporting an image model where the image's configuration can be hashed to generate a unique ID for the image and its components.
The second goal is to allow multi-architecture images, through a "fat manifest" which references image manifests for platform-specific versions of an image.
In OCI, this is codified in an [image index](image-index.md).
The third goal is to be [translatable](conversion.md) to the [OCI Runtime Specification](https://github.com/opencontainers/runtime-spec).

This section defines the `application/vnd.oci.image.manifest.v1+json` [media type](media-types.md).
For the media type(s) that this is compatible with see the [matrix](media-types.md#compatibility-matrix).

# Image Manifest

Unlike the [image index](image-index.md), which contains information about a set of images that can span a variety of architectures and operating systems, an image manifest provides a configuration and set of layers for a single container image for a specific architecture and operating system.

## *Image Manifest* Property Descriptions

- **`schemaVersion`** *int*

  This REQUIRED property specifies the image manifest schema version.
  For this version of the specification, this MUST be `2` to ensure backward compatibility with older versions of Docker. The value of this field will not change. This field MAY be removed in a future version of the specification.

- **`mediaType`** *string*

  This property SHOULD be used and [remain compatible](media-types.md#compatibility-matrix) with earlier versions of this specification and with other similar external formats.
  When used, this field MUST contain the media type `application/vnd.oci.image.manifest.v1+json`.
  This field usage differs from the [descriptor](descriptor.md#properties) use of `mediaType`.

- **`config`** *[descriptor](descriptor.md)*

    This REQUIRED property references a configuration object for a container, by digest.
    Beyond the [descriptor requirements](descriptor.md#properties), the value has the following additional restrictions:

    - **`mediaType`** *string*

        This [descriptor property](descriptor.md#properties) has additional restrictions for `config`.
        Implementations MUST support at least the following media types:

        - [`application/vnd.oci.image.config.v1+json`](config.md)

        Manifests concerned with portability SHOULD use one of the above media types.

- **`layers`** *array of objects*

    Each item in the array MUST be a [descriptor](descriptor.md).
    The array MUST have the base layer at index 0.
    Subsequent layers MUST then follow in stack order (i.e. from `layers[0]` to `layers[len(layers)-1]`).
    The final filesystem layout MUST match the result of [applying](layer.md#applying-changesets) the layers to an empty directory.
    The [ownership, mode, and other attributes](layer.md#file-attributes) of the initial empty directory are unspecified.

    Beyond the [descriptor requirements](descriptor.md#properties), the value has the following additional restrictions:

    - **`mediaType`** *string*

        This [descriptor property](descriptor.md#properties) has additional restrictions for `layers[]`.
        Implementations MUST support at least the following media types:

        - [`application/vnd.oci.image.layer.v1.tar`](layer.md)
        - [`application/vnd.oci.image.layer.v1.tar+gzip`](layer.md#gzip-media-types)
        - [`application/vnd.oci.image.layer.nondistributable.v1.tar`](layer.md#non-distributable-layers)
        - [`application/vnd.oci.image.layer.nondistributable.v1.tar+gzip`](layer.md#gzip-media-types)

        Manifests concerned with portability SHOULD use one of the above media types.
        An encountered `mediaType` that is unknown to the implementation MUST be ignored.

        Entries in this field will frequently use the `+gzip` types.

- **`refers`** *[descriptor](descriptor.md)*

    This OPTIONAL property specifies a [descriptor](descriptor.md) of another manifest.
    This value, used by the [`referrers` API](https://github.com/opencontainers/distribution-spec/blob/main/spec.md#listing-referrers), indicates a relationship to the specified manifest.

- **`annotations`** *string-string map*

    This OPTIONAL property contains arbitrary metadata for the image manifest.
    This OPTIONAL property MUST use the [annotation rules](annotations.md#rules).

    See [Pre-Defined Annotation Keys](annotations.md#pre-defined-annotation-keys).

## Example Image Manifest

*Example showing an image manifest:*
```json,title=Manifest&mediatype=application/vnd.oci.image.manifest.v1%2Bjson
{
  "schemaVersion": 2,
  "mediaType": "application/vnd.oci.image.manifest.v1+json",
  "config": {
    "mediaType": "application/vnd.oci.image.config.v1+json",
    "size": 7023,
    "digest": "sha256:b5b2b2c507a0944348e0303114d8d93aaaa081732b86451d9bce1f432a537bc7"
  },
  "layers": [
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "size": 32654,
      "digest": "sha256:9834876dcfb05cb167a5c24953eba58c4ac89b1adf57f28f2f9d09af107ee8f0"
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "size": 16724,
      "digest": "sha256:3c3a4604a545cdc127456d94e421cd355bca5b528f4a9c1905b15da2eb4a4c6b"
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "size": 73109,
      "digest": "sha256:ec4b8955958665577945c89419d1af06b5f7636b4ac3da7f12184802ad867736"
    }
  ],
  "refers": {
    "mediaType": "application/vnd.oci.image.manifest.v1+json",
    "size": 7682,
    "digest": "sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270"
  },
  "annotations": {
    "com.example.key1": "value1",
    "com.example.key2": "value2"
  }
}
```
