Helm vs Kustomize

Quick reference

	HELM	KUSTOMIZE
Approach	Templates + values	Patches on plain YAML
Packaging	Charts, versions, registries	None built in
Learning curve	A day for the basics	An hour for the basics
Per environment	`values-prod.yaml`	overlays/prod
Readable output	Render first: helm template	Plain YAML by design
Best for	Third-party and shared charts	Your own app's env changes

HELM (Charts with version history): Renders templates with your values, packaged as a versioned chart.

$helm upgrade -f values.yaml

KUSTOMIZE (Plain YAML, patched per env): Applies plain YAML with per-environment patches layered on top.

$kubectl apply -k overlays/prod

Helm → package once, install anywhere.
Kustomize → one base, an overlay per environment.

Explained

How they differ

Helm is a template engine plus a package format. You write templates with variables, set defaults in values.yaml, and override per environment. The result is a chart: a versioned artefact you can publish to a registry and install anywhere.

Kustomize is not a template engine. You keep plain YAML and describe the changes as patches and overlays: a base, then overlays/prod that edits it. kubectl apply -k reads it directly, so nothing extra is installed.

Where Helm wins

Packaging. A chart carries templates, defaults, version history and a rollback. If you install third-party software, Helm is the standard. Review. A values file is small and readable, and the template logic stays in the chart where it belongs.

Where Kustomize wins

Plain YAML. What you apply is what you can read, with no templating language to debug. Small differences. Changing replicas, image tags or limits per environment is a three-line patch.

The honest answer: use Helm to package and ship, Kustomize to adapt a base per environment. Helm can render to stdout, and Kustomize can consume the result.

The rule: choose per layer, not per company.

Templates or patches.