YAML (Yet Another Markup Language) is a human-readable data serialisation format. It uses indentation to represent structure rather than brackets or tags. It is commonly used for configuration files in Docker Compose, Kubernetes, GitHub Actions, and many other tools.

When should I use JSON vs YAML?

Use JSON for APIs and data exchange — it is universally supported and unambiguous. Use YAML for configuration files where human readability matters. YAML supports comments (JSON does not) and is easier to read for nested structures.

Are all JSON structures convertible to YAML?

Yes. Every valid JSON document is also valid YAML (YAML is a superset of JSON). This converter handles objects, arrays, strings, numbers, booleans, and null values.

JSON to YAML / YAML to JSON Converter

JSON input

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About the JSON ↔ YAML Converter

JSON and YAML both serialise structured data, but they suit different contexts. JSON is strict, compact, and supported by every programming language — it is the standard for APIs and data interchange. YAML is designed for human-readable configuration files: it supports comments, multi-line strings, and a cleaner syntax for nested structures, but is stricter about indentation and has more implicit type conversions to watch out for.

Key differences between JSON and YAML

Comments — YAML supports # comments; JSON does not.
Syntax — JSON requires quoted keys and commas. YAML uses indentation; most strings do not need quoting.
Type inference — YAML infers types (true, false, yes, no are all booleans). JSON requires explicit true/false/null.
Multi-line strings — YAML has literal (|) and folded (>) block styles. JSON requires escaped \n sequences.

When to use each format

Use JSON for API requests/responses and programmatic data interchange where strict typing matters. Use YAML for developer-facing configuration: Docker Compose, Kubernetes manifests, GitHub Actions, Ansible playbooks, and CI/CD configs where readability and comments are important.

YAML anchors and aliases

YAML supports anchors (&) and aliases (*) for reusing values and blocks within a file, reducing repetition. An anchor marks a value to be reused; an alias references it. This is particularly useful in long configuration files where the same values appear in multiple places.

Anchor syntax — default: &defaults marks a block that can be reused
Alias syntax — production: *defaults inserts the anchored block
Merge key — <<: *defaults merges an anchored mapping into the current one
Limitations — anchors and aliases are YAML-only; they are expanded and lost when converting to JSON

Frequently Asked Questions

What is the difference between JSON and YAML?

JSON requires quoted keys, braces/brackets for structure, and has no comment syntax. YAML uses indentation, allows unquoted strings, and supports # comments. JSON is better for machine parsing; YAML is better for configuration files that people read and edit. Valid JSON is also valid YAML, since YAML is a superset of JSON.

Can YAML represent everything JSON can?

Yes. YAML is a superset of JSON — all valid JSON is valid YAML. The reverse is not true: YAML features like comments, anchors (&), aliases (*), and multi-line block strings have no JSON equivalent and are dropped or expanded during YAML-to-JSON conversion.

Why does YAML convert "no" or "yes" to a boolean?

YAML 1.1 treats yes, no, on, off, true, false, y, n as booleans. This causes problems with country codes (NO for Norway) and other short words. Quote these values to keep them as strings: "no", "yes". YAML 1.2 is stricter and only recognises true/false as booleans.

How do I add comments to a JSON file?

Standard JSON does not support comments. Options: switch to YAML for your config file, use JSON5 (a superset that allows comments), use JSONC (VS Code settings format), or add a "_comment" key as a convention that will be ignored by most parsers.

How do I convert JSON to YAML in Python?

Install PyYAML: pip install pyyaml. Then: import json, yaml; data = json.loads(json_str); print(yaml.dump(data, default_flow_style=False)). To go the other way: data = yaml.safe_load(yaml_str); print(json.dumps(data, indent=2)).