How do I convert YAML to JSON?

Select YAML → JSON, paste YAML or use Upload file, and the JSON output appears. Pick a JSON indent of 2 spaces, 4 spaces, Tab or Minified, then Copy or Download.

Can it convert JSON back to YAML?

Yes. Select JSON → YAML and paste JSON. Invalid JSON shows an Invalid JSON error with the parser message. The YAML output can be copied or downloaded.

Why did yes or no turn into true or false?

By default YAML words like yes, no, on and off are read as booleans. Turn on Keep ambiguous words as text to keep them as strings, which helps for values like the country code no.

Which YAML features are not supported?

Anchors and aliases, merge keys, block scalars (| and >), and multi-document YAML with --- are not fully supported. Duplicate keys keep only the last one. A warning lists any such feature found.

Why did my leading-zero number stay as text?

Values like 007 and very large integers are kept as text so digits are not lost or changed. This avoids silent corruption, for example in IDs or zip codes.

Yes. Every tool is free to use, with no account and no credit card. The work runs on your device rather than on our servers, which is what keeps it free to run.

Does it work on mobile?

Yes. It runs in current mobile browsers on iOS and Android, with nothing to install.

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Free YAML to JSON Converter

Convert YAML to JSON and JSON to YAML in both directions. Paste in either format and get the converted output instantly — no server upload required.

Runs in your browserNo sign-up, no pop-upsNo login requiredFree forever

Works offline once loaded

JSON indent

Keep ambiguous words as text By default YAML reads yes/no/on/off/true/false as booleans. Enable this to keep them (and similar barewords) as strings — handy for config values such as the country code no. Leading zeros and very large numbers already stay strings.

YAML input

JSON output

Output will appear here…

Common uses

Convert YAML to JSON for Kubernetes ManifestsConvert Kubernetes YAML to JSON (or back) for tooling, validation scripts, or applying via the API directly.
Docker Compose YAML / JSON ConversionConvert docker-compose.yml to JSON for inspection, or back to YAML after programmatic edits.
CI/CD Pipeline Config ConversionConvert GitHub Actions, GitLab CI, CircleCI, and other pipeline configs between YAML and JSON formats.
App Configuration File ConversionConvert app config files between YAML and JSON — useful when switching frameworks or sharing configs across tools.
OpenAPI / Swagger Spec ConversionConvert OpenAPI 3.x or Swagger 2.0 API specifications between YAML and JSON. Both formats are valid and interchangeable.

How It Works

Both directions of conversion — YAML to JSON and JSON to YAML — run entirely in your browser using a hand-written parser and emitter built into the page, with no third-party YAML library and no server involved. The logic lives in a single TypeScript module (lib/yamljson.ts) that handles mappings, sequences, scalars, quoted strings, and inline comment stripping.

1
Input is preprocessed line by line
For YAML input, the parser splits the text into lines, strips inline comments (tracking quote state to avoid stripping # inside strings), measures indentation depth, and discards blank lines — building a structured list of tokens before any parsing begins.
2
A recursive descent parser builds the data tree
The parser walks the token list using indentation level to determine structure. It recognises sequence items (- value), mapping keys (key: value), and nested blocks. Scalars go through a typed coercion step that handles null, booleans, integers (rejecting leading-zero values like 007 to avoid silent data corruption), and floats — with an optional mode that keeps YAML 1.1 barewords like yes, no, on, and off as strings rather than converting them to booleans.
3
Unsupported YAML features are flagged, not silently dropped
Before emitting output, the tool scans for anchors (&name), aliases (*name), merge keys (<<:), block scalars (| and >), multi-document markers (---), and duplicate mapping keys. Any of these triggers a visible warning rather than producing subtly wrong JSON.
4
JSON is serialised or YAML is emitted, then made available
For YAML→JSON, the parsed value is passed to JSON.stringify with your chosen indentation (2 spaces, 4 spaces, tab, or minified). For JSON→YAML, a custom emitter walks the parsed JavaScript value and produces indented YAML, quoting string scalars only when necessary (e.g., values that contain :, #, or look like reserved words). Output appears instantly as you type and can be copied or downloaded.

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