Languages

YAML Cheat Sheet — Syntax Reference with Examples

YAML is indentation-based and mostly simple, with a few rules that cause most of the bugs. This sheet covers the syntax used in Docker Compose, Kubernetes, GitHub Actions, and CI configs.

Put it into practice with the matching tool.

Convert YAML and JSON →

Basics

key: valueA mapping entry — a space after the colon is required

parent:
  child: 1

Nesting by indentation (spaces only, never tabs)

# commentComment to the end of the line

{ a: 1, b: 2 }Inline (flow) mapping

---Start of a document; several can share one file

...Optional end-of-document marker

Lists

- apple
- pear

Block list

[apple, pear]Inline (flow) list

- name: web
  port: 80

List of mappings — keys align after the dash

key: []Empty list

Scalars and types

n: 42 / f: 3.14Integer / float

ok: trueBoolean (true / false)

x: null / x: ~Null; an empty value is also null

d: 2026-10-29Parsed as a date by many YAML loaders

v: "1.10"Quote to keep a string — unquoted 1.10 becomes 1.1

country: "NO"Quote to avoid YAML 1.1 reading no/yes/on/off as booleans

Strings and multi-line text

'single quotes'Literal; escape a quote by doubling it: ''

"double \n quotes"Supports escapes like \n and \t

text: |Literal block — keeps line breaks

text: >Folded block — line breaks become spaces

|- / |+Strip / keep the final newline

url: "http://a.com/#x"Quote values containing ": " or " #"

Anchors and aliases

base: &defaults
  retries: 3

Define an anchor named defaults

job: *defaultsReuse the anchored value

job:
  <<: *defaults
  retries: 5

Merge key: copy and override (not supported everywhere)

Related guides

YAML vs JSON: When to Use Each

More cheat sheets

Regex →Markdown →SQL →JS Arrays →TypeScript →JS Strings →