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YAML format rules

Indentation-sensitive data format common in Docker, Kubernetes, CI, and automation.

Format rules

  • Spaces, not tabs
  • Indentation defines nesting
  • Quotes matter for special scalars

Valid example

services:
  app:
    image: nginx

Invalid example

services:
	app:
  image: nginx

Common errors

  • Assuming YAML accepts syntax from a similar format
  • Using the wrong encoding or line ending
  • Copying invisible characters from rich text
  • Testing only the happy path and not parser errors

Online validation and conversion

Compared with nearby formats

YAML should be chosen for the parser and ecosystem that will consume it. Prefer strict formats for APIs, human-friendly formats for ops config, and signed formats only when verification is required.