- [Extensibility around core Kubernetes APIs](#extensibility-around-core-kubernetes-apis)
    - [CustomResourceDefinitions Pruning](#customresourcedefinitions-pruning)
    - [CustomResourceDefinition Defaulting](#customresourcedefinition-defaulting)
    - [CustomResourceDefinition OpenAPI Publishing](#customresourcedefinition-openapi-publishing)

In addition, users can now create multiple versions of CustomResourceDefinitions, but without any kind of automatic conversion, and CustomResourceDefinitions now allow specification of additional columns for `kubectl get` output via the `spec.additionalPrinterColumns` field.

### SIG Auth

    The `apiextensions.k8s.io/v1beta1` version of `CustomResourceDefinition` is deprecated and will no longer be served in v1.19. ([#79604](https://github.com/kubernetes/kubernetes/pull/79604), [@liggitt](https://github.com/liggitt))

* fix data loss issue if using existing azure disk with partitions in disk mount  ([#63270](https://github.com/kubernetes/kubernetes/pull/63270), [@andyzhangx](https://github.com/andyzhangx))
* The garbage collector now supports CustomResourceDefinitions and APIServices. ([#65916](https://github.com/kubernetes/kubernetes/pull/65916), [@xmudrii](https://github.com/xmudrii))

* The garbage collector now supports CustomResourceDefinitions and APIServices. ([#65918](https://github.com/kubernetes/kubernetes/pull/65918), [@nikhita](https://github.com/nikhita))

## Changes by Kind

### API Change

- The list-type of the alpha resourceClaims field introduced to Pods in 1.26.0 was modified from "set" to "map", resolving an incompatibility with use of this schema in CustomResourceDefinitions and with server-side apply. ([#114617](https://github.com/kubernetes/kubernetes/pull/114617), [@JoelSpeed](https://github.com/JoelSpeed)) [SIG API Machinery]

### Feature

## API Changes
- CustomResourceDefinitions now validate documented API semantics of `x-kubernetes-list-type` and `x-kubernetes-map-type` atomic to reject non-atomic sub-types. ([#84722](https://github.com/kubernetes/kubernetes/pull/84722), [@sttts](https://github.com/sttts))

- The list-type of the alpha `resourceClaims` field introduced to `Pods` in `1.26.0` was modified from `set` to `map`, resolving an incompatibility with use of this schema in `CustomResourceDefinitions` and with server-side apply. ([#114585](https://github.com/kubernetes/kubernetes/pull/114585), [@JoelSpeed](https://github.com/JoelSpeed))

- Removed the deprecated `azureFile` in-tree storage plugin. ([#118236](https://github.com/kubernetes/kubernetes/pull/118236), [@andyzhangx](https://github.com/andyzhangx))
- Revised `OpenAPI v2` fetching for CustomResourceDefinitions. CRDs are now aggregated lazily,
  which improves resource usage during installation of many CRDs. As a result, the first request

### **Kubernetes API**
#### User Provided Extensions
* [beta] ThirdPartyResource is deprecated. Please migrate to the successor, CustomResourceDefinition. For more information, see [Custom Resources](https://kubernetes.io/docs/concepts/api-extension/custom-resources/) and [Migrate a ThirdPartyResource to CustomResourceDefinition](https://kubernetes.io/docs/tasks/access-kubernetes-api/migrate-third-party-resource/).