# How do Helm 3 and Helm 4 apply changes to the cluster during an install or upgrade?

Helm, Hard (Expert), Concepts. https://k8wiz.com/uquiz/how-do-helm-3-and-helm-4-apply-changes-to-the-cluster-during-an-install-or-upgrade

- A. Both delete and recreate every resource on each upgrade
- B. Helm 3 uses server-side apply; Helm 4 switched to kubectl replace
- C. Helm 3 does a three-way merge; Helm 4 uses server-side apply for new releases
- D. Both diff only the new manifest against the last release, ignoring live state

**Answer:** Helm 3 does a three-way merge; Helm 4 uses server-side apply for new releases

**Explanation:** Helm 3 builds each patch from three inputs: the manifest from the previous release, the object in the cluster, and the newly rendered manifest. Helm 4 installs new releases with Kubernetes server-side apply, which tracks field ownership on the API server. On upgrade or rollback, Helm 4 keeps the release's previous apply method, so releases created by Helm 3 stay on client-side apply unless you pass --server-side.