YAML Cheat Sheet

YAML cheatsheet for YAML syntax and structures, including mappings, sequences, scalars, indentation rules, block and flow styles, block scalar (| and >) forms, anchors and aliases, merge keys, tags, and multi-document YAML streams.

Comment

A comment starts with # and continues to the end of the line.

# comment
key: value # inline comment

# metadata
title: example # stored as a plain scalar

Document Start and End

Document start is --- and document end is ... in a YAML stream.

---
key: value
...

---
apiVersion: v1
kind: ConfigMap
...

Mapping

A mapping is a set of key/value pairs; keys are typically plain scalars and values can be any YAML node.

key: value
key2: 123
nested:
  child: value

service:
  name: web
  port: 8080
  tls:
    enabled: true

Sequence

A sequence is an ordered list of items using - indicators.

- item1
- item2
- key: value

hobbies:
  - hiking
  - coding
  - movies

Flow Sequence

A flow sequence uses bracket notation and comma-separated items.

[ item1, item2, item3 ]

movies: [ "Dark Knight", "Good Will Hunting" ]

Flow Mapping

A flow mapping uses brace notation and comma-separated key/value pairs.

{ key1: value1, key2: value2 }

friend: { name: "Adam", age: 22 }

Indentation

Indentation defines structure; nested nodes are indented consistently under their parent.

parent:
  child: value
  list:
    - a
    - b

person:
  name: daniel
  friends:
    - name: steph
      age: 22

Plain Scalar

A plain scalar is an unquoted value; interpretation depends on schema/resolution.

key: plain value
key2: unquoted-string

env: production
region: us-east-1

Single-Quoted Scalar

Single quotes preserve content literally; the only escape is doubling a single quote.

key: 'literal text'
key2: 'it''s escaped by doubling'

path: 'C:\Users\name\templates'
note: 'don''t expand \n here'

Double-Quoted Scalar

Double quotes support escape sequences such as \n, \t, and \uXXXX.

key: "text"
escaped: "Line1\nLine2"
unicode: "pi: \u03C0"

message: "tab\tseparated"
file: "C:\\tmp\\file.txt"

Multiline Literal Block Scalar (|)

The literal block scalar preserves newlines and indentation as part of the value.

key: |
  line1
  line2

signature: |
  Aiman
  PHHM Organization
  email - hejes@gmail.com

Multiline Folded Block Scalar (>)

The folded block scalar folds most newlines into spaces while keeping paragraph breaks.

key: >
  line1
  line2

description: >
  Labore officia laborum Lorem culpa excepteur anim et.
  Eiusmod non quis qui tempor ea proident consectetur eiusmod
  ipsum.

Block Scalar Chomping Indicators

Chomping indicators control trailing line breaks: |- strips, | clips, |+ keeps (same for >).

clip: |
  text
strip: |-
  text
keep: |+
  text

banner_clip: |
  hello
banner_strip: |-
  hello
banner_keep: |+
  hello

Null

A null represents an explicit null value; null and ~ are commonly used.

key1: null
key2: ~

flaws: null
middle_name: ~

Boolean

Booleans are true and false (YAML 1.2 core schema).

enabled: true
disabled: false

feature_flag: true
maintenance_mode: false

Integer

Integers are whole numbers.

count: 3
negative: -21

replicas: 5
port: 8080

Float

Floats use a decimal point and/or exponent notation.

pi: 3.1415
small: 1e-6

gpa: 3.5
fav_num: 1e+10

Timestamp

Date/time scalars may be resolved as timestamps by some processors/schemas.

birthday: 2001-01-23 10:00:00

released_at: 2025-12-25 09:30:00

Explicit Tag

Tags can explicitly identify a node’s type using !!<type>.

age: !!float 18
gpa: !!str 3.5

threshold: !!float 0.75
version: !!str 1.0

Anchor (&) and Alias (*)

An anchor assigns a reusable node; an alias references the anchored node.

name: &name "daniel"
id: *name

defaults: &defaults
  retries: 3
  timeout_ms: 5000

service_a:
  config: *defaults

Merge Key (<<)

The merge key inserts key/value pairs from one or more mappings into the current mapping.

base: &base
  var1: value1

foo:
  <<: *base
  var2: value2

defaults: &defaults
  host: localhost
  port: 5432

prod:
  <<: *defaults
  host: db.example

Merge Key with Multiple Sources

A merge value can be a sequence of mappings; merges are applied in order.

base1: &base1
  a: 1
  b: 1

base2: &base2
  b: 2
  c: 2

target:
  <<: [*base1, *base2]
  c: 99

common: &common
  log_level: info
  retries: 3

region: &region
  region: eu-west-1
  retries: 5

service:
  <<: [*common, *region]
  name: api

Sequence of Mappings

A sequence can contain mappings, including flow-style mappings inside a sequence.

friends:
  - name: steph
    age: 22
  - {name: Adam, age: 22}

nodes:
  - id: n1
    role: leader
  - { id: n2, role: worker }

Mapping Value as Sequence

A mapping key can map to a sequence value.

key:
  - a
  - b

ports:
  - 80
  - 443

Multi-Document Stream

A YAML stream may contain multiple documents separated by ---.

---
kind: A
spec: {}
---
kind: B
spec: {}

---
env: dev
---
env: prod