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YAML to JSON Converter

Bi-directional, real-time conversion between YAML and JSON. Real-time parsing with syntax validation. 100% local - your data never leaves the browser.

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JSON Output
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📚 Key Terms Explained
YAML
YAML Ain't Markup Language - a human-readable data serialization language that uses indentation to define structure. Favored for configuration files in DevOps and cloud tools.
JSON
JavaScript Object Notation - a lightweight text format for representing structured data as key-value pairs, arrays, and primitives. The standard format for REST APIs and web data exchange.
Parser
Software that reads a raw text string and converts it into an in-memory data structure. A YAML parser validates indentation rules and produces a JavaScript object; a JSON parser validates brace/bracket syntax and does the same.
Serialization
The reverse of parsing: taking an in-memory object and encoding it as a text string for storage or transmission. JSON.stringify() serializes a JavaScript object to JSON; jsyaml.dump() serializes it to YAML.
Schema
A formal definition of the expected structure, types, and constraints of a data document. Both YAML and JSON have schema standards (JSON Schema, YAML Schema) used to validate that a file conforms to a required shape.
Indentation
In YAML, indentation using spaces (never tabs) is the primary syntax mechanism for defining nested structure. Unlike JSON which uses braces, YAML's entire hierarchy is conveyed through consistent 2- or 4-space indentation levels.
Key-Value Pair
The fundamental data unit in both YAML and JSON. In JSON: "name": "Alice". In YAML: name: Alice. Each key maps to exactly one value, which may itself be a string, number, boolean, null, object, or array.
Block Scalar
A YAML syntax for multi-line string values. The literal block scalar (|) preserves newlines exactly as written. The folded block scalar (>) collapses newlines into spaces unless followed by a blank line. Both are converted to a plain JSON string.
Anchor / Alias
YAML features for reusing values. An anchor (&name) marks a node; an alias (*name) references it elsewhere in the document. They eliminate repetition in large configs. During conversion, aliases are fully expanded into the JSON output.

The Complete Guide to YAML and JSON Conversion

YAML and JSON represent the same data in different ways. YAML was designed for humans writing configuration files by hand; JSON was designed for machines exchanging data over APIs. This converter lets you move freely between the two without touching a command line, server, or library installation. Everything runs directly in your browser using the battle-tested js-yaml library.

How to use this tool

Conversion is instant and automatic. Paste any YAML into the left panel and the JSON output appears on the right as you type, with no button to press. The status pill in the output panel header turns green ("Valid") when the parse succeeds, or red ("Error") when it detects a syntax problem. Hovering the red pill reveals a tooltip with the specific error message and, where available, the line number where parsing failed.

To go the other direction, click the JSON → YAML button or the swap arrows icon. The panels flip, and you can now paste JSON on the left to get YAML on the right. The Format Input button tidies up whichever format is in the left panel. Copy and Download buttons on the right panel let you extract the result without selecting text manually.

What are the main differences between YAML and JSON?

YAML and JSON are structurally equivalent for most common data shapes - objects, arrays, strings, numbers, booleans, and null - but their syntax philosophies differ dramatically. JSON is explicit and mechanical: every string must be double-quoted, every object wrapped in curly braces, every array in square brackets. This verbosity makes JSON easy to parse but verbose to write by hand. YAML trades that explicitness for readability: strings usually need no quotes, hierarchy is expressed through indentation alone, and the # comment syntax lets you annotate your configuration files.

The practical consequence is that YAML dominates configuration files - Kubernetes manifests, Docker Compose, GitHub Actions workflows, Ansible playbooks, and most CI/CD pipeline definitions are all YAML. JSON dominates REST API payloads, NoSQL document stores, package manifests (package.json), and browser-to-server data exchange.

Why comments in YAML disappear during conversion

The JSON specification has no comment syntax - this was a deliberate design decision to keep JSON parsers simple and the format unambiguous. When the YAML parser reads your document, it builds a pure data object. Comments are not data; they are discarded before the object is built. The resulting JSON output therefore has no place to put them. If you need to preserve annotations, a common workaround is to add a dedicated key like _comment with the annotation as a string value, which will survive the round-trip.

Handling complex nested structures, anchors, and block scalars

This converter handles the full YAML 1.2 feature set via js-yaml. Anchors (&name) and aliases (*name) are resolved before conversion - the JSON output contains the fully expanded data with no references. Multi-line strings written with the literal block scalar (|) are preserved as JSON strings with embedded newlines (\n). Folded block scalars (>) are collapsed per the YAML spec. Deeply nested mappings and sequences of objects are converted to their JSON object and array equivalents at every depth level.

Use cases: when to convert YAML to JSON (and back)

Frequently Asked Questions

What are the main differences between YAML and JSON? +
YAML and JSON both represent structured data as key-value pairs, but differ in syntax and purpose. JSON uses explicit braces, brackets, and double-quoted strings - precise and unambiguous but verbose. YAML uses indentation to define hierarchy - readable and writable by humans but sensitive to whitespace errors. JSON has no comment support; YAML supports # comments. JSON supports strings, numbers, booleans, arrays, objects, and null. YAML adds dates, multi-line strings, anchors, and aliases. In practice: JSON dominates REST APIs and data exchange; YAML dominates configuration files.
Why can't YAML comments be converted to JSON? +
The JSON specification (RFC 8259) has no comment syntax - this was deliberate, to keep parsers simple and the format unambiguous. When this converter parses your YAML, it builds an in-memory JavaScript object from data values only. Comments are not data and are discarded by the YAML parser before the object is constructed. The resulting JSON output has no place to put them. A common workaround is to add a dedicated key like "_comment" with the comment text as a string value, which survives the round-trip intact.
How do I handle complex nested objects in this converter? +
Complex nested YAML structures - deeply nested mappings, sequences of objects, multi-line block scalars, and anchors with aliases - are all handled automatically. Paste your YAML and the converter parses the full structure using js-yaml and outputs properly indented JSON. YAML anchors (&anchor) and aliases (*alias) are fully resolved before conversion, so the JSON output contains the expanded data. Multi-line literal block scalars (|) are preserved as JSON strings with embedded newlines. Folded scalars (>) are collapsed per the YAML spec.
Is my configuration data stored or sent anywhere? +
No. This tool runs entirely in your browser using JavaScript. Not one character of your YAML or JSON is transmitted to any server, logged, or stored. Conversion happens locally in your browser's JavaScript engine. Your Kubernetes configs, Docker Compose files, API secrets, and application settings remain completely on your machine. You can save this page as an HTML file and run it offline with no network connection - it will work identically.
Can I convert JSON arrays back to valid YAML? +
Yes. Click the "JSON to YAML" direction button, paste your JSON on the left, and the converter outputs clean YAML on the right. JSON arrays become YAML sequences (list items prefixed with - ). Nested JSON objects become indented YAML mappings. Strings, numbers, booleans, and null use YAML's native literal syntax. The output uses 2-space indentation, which is the most widely accepted YAML convention for configuration files.