.yaml

What is a .yaml file?

YAML is a human-readable configuration format using indentation instead of brackets — the standard for Docker, Kubernetes, GitHub Actions, and CI/CD pipelines.

Safe format
Type Data
By Clark Evans
MIME application/x-yaml

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What is it

You're editing a configuration file. It uses indentation instead of curly braces, has no commas, and looks almost like a plain-text outline. That's YAML — the format that won the DevOps world by being easier to read than JSON or XML. At least until a whitespace error breaks your entire deployment.

YAML is the de facto standard for infrastructure configuration: Docker Compose files, Kubernetes manifests, GitHub Actions workflows, Ansible playbooks, and CI/CD pipelines are all YAML. The format is deceptively powerful — it supports references, anchors, multi-line strings, and complex nested structures. It's also deceptively fragile. Indentation is syntactic, and YAML uses spaces only (not tabs). A single misaligned key can cause a silent misconfiguration or a noisy failure.

Any text editor opens YAML. VS Code with the YAML extension provides schema validation, which catches indentation errors before they reach production. For learning the format, the official spec is surprisingly readable. The practical rule: copy a working example, modify it carefully, and never mix tabs and spaces.

Technical details
Full Name
YAML Ain't Markup Language
MIME Type
application/x-yaml
Developer
Clark Evans
Magic Bytes
N/A
Safety
.yaml is a known, safe format.
What opens it
Any text editor
FREE All
VS Code
FREE All
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.
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