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What is it
YAML is a human-readable configuration format that uses indentation instead of brackets — the de facto standard for DevOps tools like Docker Compose, Kubernetes, and GitHub Actions. Config files for humans. YAML is cleaner to read than JSON or XML — at least until you get bitten by a whitespace error. The format is surprisingly powerful (it supports references, anchors, and multi-line strings) and surprisingly fragile (a single misplaced space breaks everything). Love it or hate it, if you work in infrastructure, you will write a lot of YAML.
Technical details
Safety
What opens it
Any text editor
VS Code
FAQ
What's the difference between YAML and JSON?
YAML is more human-readable (no brackets, supports comments). JSON is more machine-friendly (strict syntax, no ambiguity). YAML is a superset of JSON — every valid JSON file is also valid YAML.
What's the difference between YAML and TOML?
TOML uses explicit key-value pairs and is harder to mess up with whitespace. YAML is more expressive but more error-prone. TOML is gaining popularity for simpler configs (Rust's Cargo.toml, Python's pyproject.toml).
How do I validate a YAML file?
Use an online YAML validator, or run it through a linter in your editor (VS Code's YAML extension catches errors in real time). The most common mistake is inconsistent indentation — use spaces, never tabs.
Related formats