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Webhooks are requests for information sent in a blocking fashion. A web application implementing webhooks will send a HTTP request to other applications when a certain event happens.

In the kubernetes world, there are 3 kinds of webhooks: admission webhook, authorization webhook and CRD conversion webhook.

In controller-runtime libraries, we support admission webhooks and CRD conversion webhooks.

Kubernetes supports these dynamic admission webhooks as of version 1.9 (when the feature entered beta).

Kubernetes supports the conversion webhooks as of version 1.15 (when the feature entered beta).

Supporting older cluster versions

By default, kubebuilder create webhook will create webhook configs of API version v1, a version introduced in Kubernetes v1.16. If your project intends to support Kubernetes cluster versions older than v1.16, you must use the v1beta1 API version:

kubebuilder create webhook --webhook-version v1beta1 ...