Go Template Basics

Helm renders templates with Go's template engine — double curly braces inject values into your YAML.

Syntax{{ .Values.someKey }}

Helm templating is built on the Go template language. Anything inside {{ }} is an action — an expression Helm evaluates and replaces with text.

The rendering flow

Helm merges your values with the chart's built-in objects, then walks each template file replacing actions with computed strings. The output is plain Kubernetes YAML.

values.yaml plus templates are combined by the engine into rendered manifestsvalues.yamltemplates/templateenginerenderedmanifests
Values and templates flow through the engine to produce final Kubernetes manifests.

Actions vs text

Everything outside {{ }} is copied verbatim. So your files look like normal YAML with small template snippets sprinkled in.

Example

Example · yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: {{ .Release.Name }}-config
data:
  greeting: {{ .Values.greeting }}
  env: {{ .Values.environment }}

When to use it

  • A chart author uses {{ .Values.image.tag }} in a Deployment template so operators can pin a specific container image version without editing any manifest directly.
  • A developer uses {{ if .Values.ingress.enabled }} to conditionally render an Ingress resource only when the operator opts in by setting the value to true.
  • A platform engineer uses helm template to render a chart locally with production values and diff the output against what is currently deployed, catching regressions before they reach the cluster.

More examples

Inject a value into YAML

Shows the fundamental pattern: double-brace expressions are replaced with values at render time, producing plain Kubernetes YAML.

Example · yaml
# templates/deployment.yaml
metadata:
  name: {{ .Release.Name }}-web
spec:
  replicas: {{ .Values.replicaCount }}
  template:
    spec:
      containers:
        - image: {{ .Values.image.repository }}:{{ .Values.image.tag }}

Conditional block in template

Uses an if block to include the loadBalancerIP field only when the service type is LoadBalancer.

Example · yaml
# templates/service.yaml
spec:
  type: {{ .Values.service.type }}
  {{- if eq .Values.service.type "LoadBalancer" }}
  loadBalancerIP: {{ .Values.service.loadBalancerIP }}
  {{- end }}

Render chart locally

Renders all templates to stdout without contacting Kubernetes, useful for reviewing the final YAML before applying.

Example · bash
helm template my-release ./myapp \
  --set image.tag=v2.1.0 \
  -f values-staging.yaml

Related

helm builtin objectshelm pipelines

Discussion

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