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What is a YAML file?
YAML is an indentation-based data format designed to be easier for humans to write than JSON, and it is a superset of it. It supports comments and reusable anchors, which is why it dominates CI pipelines and infrastructure configuration. Indentation errors are its classic failure mode.
At a glance
- Full name
- YAML Ain't Markup Language
- Extensions
- .yaml, .yml
- Type
- Data
- Introduced
- 2001
- Created by
- Clark Evans, Ingy döt Net, Oren Ben-Kiki
- Compression
- None
- MIME type
- application/yaml
Strengths
- Supports comments, unlike JSON
- Less punctuation, so configuration reads more cleanly
- Anchors and aliases let you reuse blocks
Limitations
- Whitespace-sensitive, so indentation mistakes break files silently
- The full specification is large and implementations differ
- Ambiguous scalars: unquoted values can parse as unexpected types
When to use YAML
Use it when
Human-edited configuration: CI pipelines, Kubernetes, application config.
Avoid it when
Machine-to-machine payloads where JSON is simpler and faster to parse.
Convert YAML files
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YAML conversions
Each page states what the target format cannot carry before you run it.
YAML compared
Related data formats
Last updated 2026-08-03