YAML to JSON & JSON to YAML Converter — Free & Local

Guide

About YAML ↔ JSON

Bidirectional YAML ↔ JSON conversion that auto-detects which direction to go from the input. Validates as it parses, so you get a precise error before any conversion. Indent control on YAML output (2 / 4 spaces). Comments are preserved through round-trips when the source format supports them.

YAML vs JSON: when to use which

YAML is human-readable; JSON is machine-parseable. Most config in 2026 starts as YAML (Kubernetes manifests, GitHub Actions, Docker Compose, Ansible) and gets converted to JSON inside tooling for processing. Round-tripping between the two is a daily move.

	YAML	JSON
Readability	High — indentation, no braces, comments allowed	Lower — braces, quotes, no comments
Comments	Yes (`#`)	No
Multi-line strings	Yes (`	`,` >`)
Parse speed	Slower	Faster
Ambiguity	Higher (the `NO` → `false` trap)	Low, one canonical form
Best for	Files humans edit	Machine-to-machine data

Rule of thumb: YAML for humans, JSON for machines. YAML wins on readability and usability for hand-edited config; JSON wins on speed, determinism, and native support in every language. Since YAML is a superset of JSON, any JSON document is already valid YAML — which is why conversion in this direction is lossless and the reverse only drops comments. TOML is a third choice, clearer than both for small, flat application config but weaker for deeply nested data.

Conversion details that matter

Anchors and aliases. YAML lets you reuse blocks via &base and *base. JSON has no such concept — anchors get inlined, aliases get expanded into copies. The result is more verbose JSON but identical semantics.
Tags. Explicit YAML tags like !!str are honored. !!int and !!float ensure correct typing in the JSON output.
Multiline strings. |-style block scalars become regular JSON strings with \n escapes. Round-trip back to YAML and you get the same block style.
Booleans. We default to YAML 1.2 strict booleans (true/false only). Older configs may expect yes/no to parse as boolean — toggle YAML 1.1 mode for that.

How to convert YAML to JSON in code and CLI

Test the shape here, then automate with one of these:

Python (PyYAML):

import yaml, json
json.dump(yaml.safe_load(open("in.yaml")), open("out.json", "w"), indent=2)

CLI (yq) — the fastest path for files and pipelines:

yq -o=json '.' in.yaml > out.json      # YAML → JSON
yq -P '.' in.json > out.yaml           # JSON → YAML

Node / npm — npm i js-yaml, then JSON.stringify(yaml.load(fs.readFileSync("in.yaml","utf8")), null, 2).

VS Code — install the YAML (Red Hat) extension; the command palette’s Convert helpers plus paste-as-JSON cover the json to yaml in vs code workflow without leaving the editor.

Converting OpenAPI and Swagger specs

OpenAPI/Swagger specs ship in either format, and toolchains disagree on which they accept. Paste your openapi.yaml here to get openapi.json for a tool that only reads JSON (or the reverse for one that wants YAML). Anchors get inlined and tags resolved, so the output validates against the same schema — no manual reflow. For very large specs, yq -o=json openapi.yaml does the same on the command line.

Common workflows

Inspect a Kubernetes manifest. Paste the YAML, see the JSON. The JSON form is what kubectl actually sends — useful for debugging.

Translate a Compose file. Docker Compose v3 is YAML; many tools want JSON. Paste, copy the JSON, feed it forward.

Convert config snippets in PRs. Copy the YAML from a code review comment, see what fields it actually populates. Faster than running the full validation pipeline.

Sanity-check generated YAML. A code generator emits YAML; round-trip it through JSON and back. The two YAMLs should be value-equivalent — if not, the generator is producing something the parser does not see.

Why our converter avoids the YAML 1.1 trap

The classic YAML footgun: country: NO parses as country: false. The Norwegian Country Code Catastrophe. Our default is YAML 1.2 — NO stays a string. If you genuinely need the old behavior (legacy Ansible, old Compose files), the toggle is one click away. Most modern YAML is 1.2-or-stricter; defaulting accordingly avoids the most common bug.

Frequently asked questions

How is direction auto-detected?

We try parsing as YAML first (it is a superset of JSON for our purposes). If the input is valid JSON, we convert to YAML; otherwise we treat it as YAML and convert to JSON. You can pin direction with the toggle.

Does it preserve comments?

YAML supports comments; JSON does not. YAML → JSON drops comments. JSON → YAML inserts them only if you provide a hint (we do not invent commentary). For round-trip preservation, edit YAML directly.

What YAML version is supported?

YAML 1.2 (the modern spec). Includes anchors and aliases (&ref / *ref), block and flow styles, multiline strings (| literal, > folded), explicit tags.

Why does <code>NO</code> become <code>false</code> in my JSON?

YAML 1.1 (the older spec, still common) treats YES, NO, ON, OFF as booleans. We default to YAML 1.2 (only true/false are booleans) — toggle YAML 1.1 mode if your input depends on the older behavior.

Can it format multiline strings?

Yes. Block scalars (| for newline-preserving, > for folded) survive round-trips and are emitted by default for any string containing newlines longer than a threshold.

How does it handle big YAML files?

Parsing runs on a Web Worker. Files in the 1-10 MB range convert instantly. Above that, prefer command-line yq for streaming.

How do I convert YAML to JSON in Python?

Use PyYAML plus the stdlib JSON module: import yaml, json; json.dump(yaml.safe_load(open("in.yaml")), open("out.json","w"), indent=2). Always use safe_load, not load — the latter can execute arbitrary tags. This tool does the same conversion with no install and nothing leaving your browser.

When should I use YAML vs JSON?

Use YAML for files humans edit — config, CI pipelines, Kubernetes manifests — because it allows comments, multi-line strings, and anchors, and is less noisy. Use JSON for machine-to-machine data — APIs, logs, storage — because it parses faster, has one canonical form, and every language reads it natively. YAML is a superset of JSON, so any JSON is already valid YAML. (TOML is a third option, better than both for small, flat app config.)

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Last updated: 2026-07-04