📄 YAML Ultimate Guide

A human-readable, whitespace-sensitive format for configuration & data serialization.

A serialization language is a format used to convert complex data structures (objects, arrays, etc.) into a flat format (text or binary).

🔧 Core Rules

🧱 Data Types

🔹 Key-Value Pair

app: Eventra
port: 3000
version: "1.0"

🔹 Nested Object

database:
  host: localhost
  port: 5432
  credentials:
    username: admin
    password: "pa$$word"

🔹 List (Array)

Hyphen method

services:
  - web
  - api
  - auth

Inline method

services: [web, api, auth]

🔤 Scalars (Simple Data Types)

string: Hello World
number: 42
float: 99.99
boolean_true: true     # also yes, on
boolean_false: false   # also no, off
null_value: null       # or just leave blank

🧾 Multiline Strings

Literal block (|) – preserves line breaks

description: |
  This is line 1.
  This is line 2.

Folded block (>) – folds into one line

note: >
  This is line 1
  and line 2 will join.

🔁 Anchors & Aliases (Reusability)

default: &default-env
  DEBUG: false
  PORT: 8080

dev:
  <<: *default-env
  DEBUG: true

⚙️ Environment Variables

env: $NODE_ENV         # shell style
config: "{{ value }}"  # templating (e.g. Ansible/Helm)

🗂️ Comments

# This is a comment

📚 Multiple Documents in One File

---
app: one
port: 3000
---
app: two
port: 4000

🔄 YAML vs JSON vs XML (Mini-Comparison)

🐳 Docker Compose YAML (Example)

version: "3.8"
services:
  app:
    image: node:18
    ports:
      - "3000:3000"
    environment:
      - NODE_ENV=production
    volumes:
      - ./app:/usr/src/app

☸️ Kubernetes Pod YAML (Example)

apiVersion: v1
kind: Pod
metadata:
  name: eventra-app
spec:
  containers:
    - name: backend
      image: node:18
      ports:
        - containerPort: 3000

🤖 GitHub Actions YAML (CI/CD Example)

name: Build & Deploy
on:
  push:
    branches: [main]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Install deps
        run: npm install
      - name: Build
        run: npm run build

🔥 Pro Tips

• Use .yml or .yaml (both valid)

• Keep consistent 2-space or 4-space indentation

• Use double quotes when using special characters

• Use --- to split multiple components

• Anchor (&) and alias (*) for DRY configs

✅ When to Use YAML?