YAML vs JSON: What's the Difference and When to Use Each

#javascript #json #webdev #programming

If you've worked with config files, Docker, Kubernetes, or any CI/CD system, you've encountered YAML. If you've built APIs, you know JSON. But when should you use which?

The Syntax Difference

JSON:

{
  "name": "my-app",
  "version": "1.0.0",
  "features": {
    "auth": true,
    "cache": false
  },
  "ports": [3000, 8080]
}

YAML (same data):

name: my-app
version: 1.0.0
features:
  auth: true
  cache: false
ports:
  - 3000
  - 8080

YAML is less verbose and more readable. But it has strict indentation rules.

YAML Gotchas

1. Indentation matters (use spaces, not tabs)

# Wrong
parent:
    child: value  # Tab indented - BROKEN

# Correct
parent:
  child: value  # 2 spaces - WORKS

2. Strings don't need quotes... but sometimes do

version: "1.0"     # Quotes needed - without quotes, YAML reads 1.0 as a float
enabled: "true"    # Quotes needed - without, YAML reads as boolean
port: 3000         # No quotes needed for integers

3. Multi-line strings

description: |
  This is a multi-line
  string that preserves
  newlines.

summary: >
  This is a multi-line
  string that becomes
  one line.

When to Use Each

Use Case	Format	Why
Config files	YAML	More readable, comments allowed
Docker Compose	YAML	Standard
Kubernetes	YAML	Standard
REST API responses	JSON	Universally supported
Package.json	JSON	Node.js standard
Database storage	JSON	No indentation issues
CI/CD pipelines	YAML	Standard (GitHub Actions, etc.)