YAML Linter - Online YAML Validator & Syntax Checker

What is a YAML Linter?

A YAML linter is a tool that scans your YAML configuration files for syntax errors, invalid indentation, and structural issues before they cause runtime failures. YAML is whitespace-sensitive, so a single misplaced space can break a Kubernetes deployment or CI/CD pipeline.

Why Use This YAML Linter?

Common YAML Syntax Errors

Indentation Issues

YAML uses spaces for indentation (not tabs). Inconsistent indentation is the most common error:

# Wrong - mixed indentation
spec:
  containers:
    - name: app
       image: nginx  # Extra space causes error

# Correct
spec:
  containers:
    - name: app
      image: nginx

Missing Colons or Quotes

# Wrong - missing colon
metadata
  name: my-app

# Wrong - unquoted special characters
env:
  value: ${VAR}  # Should be quoted

# Correct
metadata:
  name: my-app
env:
  value: "${VAR}"

Duplicate Keys

# Wrong - duplicate keys
metadata:
  name: first
  name: second  # Will overwrite first

# Correct - use unique keys
metadata:
  name: my-app
  namespace: default

Typical Use Cases

Kubernetes Manifests

Validate Deployments, Services, ConfigMaps, and other K8s resources before applying:

# Instead of discovering errors at apply time
kubectl apply -f deployment.yaml

# Lint first with this tool, then apply

Helm Chart Values

Check values.yaml and override files for syntax errors before helm install:

# values.yaml
replicaCount: 3
image:
  repository: nginx
  tag: "1.21"
  pullPolicy: IfNotPresent

CI/CD Pipelines

Validate GitHub Actions, GitLab CI, Azure Pipelines, and other CI/CD configs:

# .github/workflows/ci.yml
name: CI
on: [push, pull_request]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm test

Application Configuration

Lint application configs like Docker Compose, Ansible playbooks, or custom YAML:

# docker-compose.yml
services:
  web:
    image: nginx
    ports:
      - "80:80"

Kubernetes Profile Checks

When using the Kubernetes manifest profile, the linter performs additional structural checks:

• Verifies apiVersion and kind are present
• Checks for metadata.name on all resources
• Validates spec.template.spec.containers for Deployments/StatefulSets/DaemonSets
• Warns about missing spec.selector.matchLabels
• Checks Service spec.ports and optional spec.selector

Privacy & Security

All processing happens directly in your browser:

• No Server Communication: Your YAML data never leaves your device
• No Storage: Nothing is saved to localStorage, cookies, or servers
• Open Source: All code is transparent and auditable

Related Tools

Explore our other DevOps tools:

• JSON Linter - Validate JSON syntax and structure
• YAML/JSON Path Tester - Test JSONPath expressions
• kubectl Builder - Visual kubectl command builder
• JWT Tools - Decode and create JSON Web Tokens

Need help? All code is open-source. Visit our GitHub or contact us with questions or feedback.