YAML Guide: Syntax, Examples, and Best Practices

YAML is a human-readable data serialization format. It is widely used for configuration files in Docker, Kubernetes, GitHub Actions, Ansible, and many other tools.

Basic Syntax

YAML uses indentation (spaces, not tabs) to structure data. Key-value pairs use colons.

name: Alice
age: 30
active: true

Data Types

string: hello world
quoted: "value with special chars: yes"
number: 42
float: 3.14
boolean: true
null_value: null
date: 2024-01-15

Lists (Arrays)

fruits:
  - apple
  - banana
  - cherry

# Inline format
colors: [red, green, blue]

Nested Objects

person:
  name: Alice
  address:
    city: New York
    country: USA
  hobbies:
    - reading
    - coding

Multi-line Strings

# Literal block (preserves newlines)
description: |
  First line
  Second line
  Third line

# Folded block (converts newlines to spaces)
summary: >
  This is a long sentence
  that spans multiple lines
  but becomes one line.

Anchors and Aliases (Reuse)

defaults: &defaults
  timeout: 30
  retries: 3

development:
  <<: *defaults
  host: localhost

production:
  <<: *defaults
  host: prod.example.com

Comments

# This is a comment
name: value  # Inline comment

Common Use Cases

Docker Compose - defining multi-container applications
Kubernetes - pod, service, and deployment configs
GitHub Actions - CI/CD workflow definitions
Ansible - infrastructure automation playbooks
Config files - application settings

YAML vs JSON

YAML supports comments, JSON does not
YAML uses indentation, JSON uses braces
YAML is more human-readable, JSON is more machine-readable
YAML can reference other parts of the document (anchors)

Convert YAML to JSON

Need to convert YAML to JSON? Use the YAML to JSON converter to instantly convert your YAML configuration to JSON format.

Common Mistakes

Using tabs instead of spaces (causes parse errors)
Mixing tabs and spaces
Forgetting colons after keys
Not quoting strings that contain special characters (:, { , } , [, ])

YAML Guide: Syntax and Examples