What are the basic syntax in YAML?

key: value — Key-value pair (space after colon required); # comment — Comment (hash to end of line); --- — Document start marker; ... — Document end marker; name: "hello world" — Quoted string (preserves special chars); count: 42 — Integer; price: 9.99 — Float; active: true — Boolean (true/false, yes/no, on/off); empty: null — Null value (null or ~); date: 2026-03-06 — Date (ISO 8601)

What are the sequences (lists) in YAML?

- item1 - item2 - item3 — Block sequence (one item per line); items: [a, b, c] — Flow sequence (inline, JSON-style); - name: Alice age: 30 — Sequence of mappings; - - a - b — Nested sequences

What are the mappings (objects) in YAML?

key: value — Simple mapping; parent: child: value — Nested mapping (2-space indent); {name: Alice, age: 30} — Flow mapping (inline, JSON-style); ? complex key : value — Complex key syntax

YAML Cheat Sheet

Quick reference for YAML syntax: scalars, sequences, mappings, anchors, multi-line strings, and common patterns for config files, Docker Compose, and CI/CD.

Basic Syntax Sequences (Lists) Mappings (Objects) Multi-line Strings Anchors & Aliases Common Patterns

Basic Syntax

key: value	Key-value pair (space after colon required)
# comment	Comment (hash to end of line)
---	Document start marker
...	Document end marker
name: "hello world"	Quoted string (preserves special chars)
count: 42	Integer
price: 9.99	Float
active: true	Boolean (true/false, yes/no, on/off)
empty: null	Null value (null or ~)
date: 2026-03-06	Date (ISO 8601)

Sequences (Lists)

- item1 - item2 - item3	Block sequence (one item per line)
items: [a, b, c]	Flow sequence (inline, JSON-style)
- name: Alice age: 30	Sequence of mappings
- - a - b	Nested sequences

Mappings (Objects)

key: value	Simple mapping
parent: child: value	Nested mapping (2-space indent)
{name: Alice, age: 30}	Flow mapping (inline, JSON-style)
? complex key : value	Complex key syntax

Multi-line Strings

text: \| line 1 line 2	Literal block (preserves newlines)
text: > line 1 line 2	Folded block (joins lines with space)
text: \|+	Literal block, keep trailing newlines
text: \|-	Literal block, strip final newline
text: >-	Folded block, strip final newline

Anchors & Aliases

defaults: &defaults timeout: 30	Define anchor with &name
server: <<: *defaults	Merge anchor with <<: *name
other: *defaults	Reference anchor with *name

Common Patterns

env: - name: DB_HOST value: localhost	Kubernetes env vars style
services: web: image: nginx	Docker Compose service
jobs: build: runs-on: ubuntu-latest	GitHub Actions job
stages: - build - test - deploy	CI/CD pipeline stages
matrix: node: [16, 18, 20]	Build matrix (GitHub Actions)

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