Comparison
Kustomize vs Helm
Kustomize and Helm both help you manage Kubernetes manifests, but they take very different approaches. Kustomize patches and overlays existing YAML without templating. Helm renders YAML from Go templates and a values file. This page compares the two and offers practical conversion guidance. Kustomize Helper includes tools that work with the Kustomize model, all in your browser.
What is Kustomize?
Kustomize is a manifest transformer built into kubectl (kubectl apply -k). It takes a set of existing YAML resources and applies structured transformations: namePrefix and nameSuffix, commonLabels and commonAnnotations, namespace, image overrides, configMap and secret generators, and patches. There are no templates and no values file. The input and output are both plain YAML, which makes changes easy to review in a diff.
What is Helm?
Helm is a package manager for Kubernetes. A chart is a collection of Go templates plus a values file. Helm renders the templates with the supplied values to produce the final YAML. Charts are versioned and publishable to repositories, and Helm tracks releases so you can rollback to a previous version. The rendering step is powerful but opaque: the diff between two versions is in the rendered output, not always in the chart source.
Side by side
| Concern | Kustomize | Helm |
|---|---|---|
| Model | Patch and overlay existing YAML | Render templates from values |
| Input format | Plain YAML | Go templates plus values.yaml |
| Packaging | Folders, no chart repository | Versioned charts, repositories |
| Release tracking | No (use Git) | Yes, with rollback |
| Environment overlays | First-class base/overlay model | Separate values files per env |
| Reviewability | High: patches are diff-like | Lower: rendered output is the diff |
| Best for | Internal apps, env-specific config | Third-party charts, shared distributions |
When to choose Kustomize
- You own the manifests and want them reviewable in a Git diff.
- You need per-environment overlays on top of a shared base.
- You want to avoid templating logic and keep YAML declarative.
- You already use kubectl and want to apply with kubectl apply -k without an extra tool.
When to choose Helm
- You install third-party software that ships as a chart.
- You want release tracking and rollback built in.
- You need parameterized rendering for many configurations.
- You distribute your own application as a versioned package.
Converting Helm values to Kustomize patches
- Render the chart once with your current values: helm template my-release ./chart -f values.yaml > rendered.yaml.
- Split rendered.yaml into base resource files (Deployment, Service, etc.) and place them in a base/ folder.
- Create a base/kustomization.yaml that lists those resources. The Kustomization Builder on this site can generate that file for you.
- For each environment, create an overlay folder that references ../../base and applies patches for the fields you used to override via values.
- Use the Overlay Generator on this site to scaffold the base/overlay tree, then paste your rendered resources into the base files.
Try the Overlay Generator or the Kustomization Builder to do this in your browser.