YAML in 10 Minutes

YAML is a human-friendly data format — like JSON but with less punctuation.

The 6 rules

1. Indentation matters — 2 spaces per level. Never use tabs.
2. key: value is a mapping.
3. - item is a list item.
4. Strings usually don't need quotes.
5. # starts a comment.
6. --- separates multiple documents in one file.

A working example (Kubernetes-ish)

apiVersion: v1
kind: Pod
metadata:
  name: web
  labels:
    app: nginx
    tier: frontend
spec:
  containers:
    - name: nginx
      image: nginx:1.27
      ports:
        - containerPort: 80
      env:
        - name: LOG_LEVEL
          value: info

Tricky parts

• Strings that look like booleans or numbers can bite you:

  version: 3.10     # this is 3.1 (a float!)  Use "3.10" as string.
  release: yes      # this is boolean true (weird YAML 1.1)  Use "yes".
  

• Anchors (advanced) let you reuse blocks:

  defaults: &defaults
    timeout: 30
    retries: 3
  api:
    <<: *defaults
    endpoint: /api
  

Real-world example

Docker Compose, GitHub Actions, Ansible, Kubernetes, Helm — you'll write YAML every single day. Install a YAML linter in your editor and you'll never miss an indent.