- CRD supports multi-version Schema, Subresources and AdditionalPrintColumns (NOTE that CRDs created prior to 1.13 populated the top-level additionalPrinterColumns field by default. To apply an updated that changes to per-version additionalPrinterColumns, the top-level additionalPrinterColumns field must be explicitly set to null). ([#702...

- The example API server has renamed its `wardle.k8s.io` API group to `wardle.example.com` ([#81670](https://github.com/kubernetes/kubernetes/pull/81670), [@liggitt](https://github.com/liggitt))
- CRDs defaulting is promoted to GA. Note: the feature gate CustomResourceDefaulting will be removed in 1.18. ([#84713](https://github.com/kubernetes/kubernetes/pull/84713), [@sttts](https://github.com/sttts))

    - [API Machinery](#api-machinery)
      - [kube-apiserver](#kube-apiserver)
      - [Dynamic Admission Control](#dynamic-admission-control)
      - [Custom Resource Definitions (CRDs)](#custom-resource-definitions-crds)
      - [Garbage Collector](#garbage-collector)
      - [Monitoring/Prometheus](#monitoringprometheus)
      - [Go Client](#go-client)
  - [External Dependencies](#external-dependencies)

- Fixed a bug that prevents kubectl to validate CRDs with schema using x-kubernetes-preserve-unknown-fields on object fields.

* 'cj' has been added as a shortname for CronJobs, as in `kubectl get cj` ([#59499](https://github.com/kubernetes/kubernetes/pull/59499), [@soltysh](https://github.com/soltysh))

* `crds` has been added as a shortname for CustomResourceDefinition, as in `kubectl get crds` ([#59061](https://github.com/kubernetes/kubernetes/pull/59061), [@nikhita](https://github.com/nikhita))

- 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
  to fetch the OpenAPI may be slower. ([#118808](https://github.com/kubernetes/kubernetes/pull/118808), [@Jefftree](https://github.com/Jefftree))

- Reduce API server memory when many CRDs are loaded by sharing a single etcd3 client logger across all clients ([#111648](https://github.com/kubernetes/kubernetes/pull/111648), [@negz](https://github.com/negz)) [SIG API Machinery]

- Fixed a bug that prevents kubectl to validate CRDs with schema using x-kubernetes-preserve-unknown-fields on object fields.

  For more information, see [#53006](https://github.com/kubernetes/kubernetes/issues/53006).

*   Custom Resource Definitions (CRDs) are not properly deleted under certain conditions. This issue will be fixed in a future release.

  For more information, see [#56348](https://github.com/kubernetes/kubernetes/issues/56348).

- Reduce API server memory when many CRDs are loaded by sharing a single etcd3 client logger across all clients ([#111650](https://github.com/kubernetes/kubernetes/pull/111650), [@negz](https://github.com/negz)) [SIG API Machinery]