JSON vs YAML: Key Differences
| Feature | JSON | YAML |
|---|---|---|
| Syntax | Brackets & braces | Indentation-based |
| Readability | Good | Excellent |
| Comments | Not allowed | Supported with # |
| Data types | Basic types | More types (dates, etc.) |
| File size | Slightly larger | More compact |
| Use cases | APIs, data exchange | Configuration files |
When to use YAML:
- Kubernetes manifests
- Docker Compose files
- CI/CD pipelines (GitHub Actions, GitLab CI)
- Ansible playbooks
- Human-edited configuration
Convert JSON to YAML in JavaScript
Use the js-yaml library for reliable conversion:
javascript
// npm install js-yaml
const yaml = require('js-yaml');
const jsonData = {
apiVersion: "v1",
kind: "Pod",
metadata: {
name: "my-pod",
labels: {
app: "web"
}
},
spec: {
containers: [
{
name: "nginx",
image: "nginx:latest",
ports: [{ containerPort: 80 }]
}
]
}
};
// Convert to YAML
const yamlString = yaml.dump(jsonData, {
indent: 2,
lineWidth: -1, // Don't wrap long lines
noRefs: true, // Don't use YAML references
sortKeys: false // Keep key order
});
console.log(yamlString);
/*
apiVersion: v1
kind: Pod
metadata:
name: my-pod
labels:
app: web
spec:
containers:
- name: nginx
image: nginx:latest
ports:
- containerPort: 80
*/
// Convert JSON string to YAML
function jsonToYaml(jsonString) {
const data = JSON.parse(jsonString);
return yaml.dump(data);
}Convert JSON to YAML in Python
Python's PyYAML library handles the conversion:
python
# pip install pyyaml
import yaml
import json
json_data = {
"apiVersion": "v1",
"kind": "Service",
"metadata": {
"name": "my-service"
},
"spec": {
"selector": {
"app": "web"
},
"ports": [
{"port": 80, "targetPort": 8080}
]
}
}
# Convert to YAML
yaml_string = yaml.dump(json_data,
default_flow_style=False, # Use block style
sort_keys=False, # Preserve key order
allow_unicode=True
)
print(yaml_string)
# Convert JSON file to YAML file
def json_to_yaml_file(json_path, yaml_path):
with open(json_path, 'r') as f:
data = json.load(f)
with open(yaml_path, 'w') as f:
yaml.dump(data, f, default_flow_style=False)
# Convert JSON string to YAML
def json_to_yaml(json_string):
data = json.loads(json_string)
return yaml.dump(data, default_flow_style=False)Command Line Conversion
Convert JSON to YAML using CLI tools:
bash
# Using yq (install: brew install yq)
yq -P input.json > output.yaml
# Using Python one-liner
python -c "import yaml,json,sys; print(yaml.dump(json.load(sys.stdin), default_flow_style=False))" < input.json > output.yaml
# Using Node.js with js-yaml
npx js-yaml input.json > output.yaml
# Convert all JSON files in directory to YAML
for f in *.json; do
yq -P "$f" > "${f%.json}.yaml"
done
# Using jq + yq together
cat input.json | yq -PKubernetes JSON to YAML
Converting Kubernetes manifests from JSON to YAML:
javascript
// Kubernetes Deployment JSON
const deployment = {
apiVersion: "apps/v1",
kind: "Deployment",
metadata: {
name: "web-app",
labels: { app: "web" }
},
spec: {
replicas: 3,
selector: {
matchLabels: { app: "web" }
},
template: {
metadata: {
labels: { app: "web" }
},
spec: {
containers: [{
name: "web",
image: "nginx:1.21",
ports: [{ containerPort: 80 }],
resources: {
limits: { cpu: "500m", memory: "128Mi" },
requests: { cpu: "250m", memory: "64Mi" }
}
}]
}
}
}
};
// Using kubectl to convert
// kubectl get deployment my-app -o yaml > deployment.yaml
// Or use our JSON to YAML tool online!Frequently Asked Questions
Why use YAML instead of JSON for Kubernetes?
YAML is more readable, supports comments for documentation, and is the standard format for Kubernetes manifests. Most K8s examples and tools use YAML.
Is YAML a superset of JSON?
Yes! Valid JSON is also valid YAML. YAML parsers can read JSON files directly, but YAML has additional features like comments and anchors.
How do I preserve key order when converting?
Use sortKeys: false in js-yaml or sort_keys=False in PyYAML to maintain the original key order from JSON.
Can I convert YAML back to JSON?
Yes! Use our YAML to JSON converter or libraries like js-yaml (yaml.load) and PyYAML (yaml.safe_load).