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YAML ↔ JSON Converter

Convert between YAML and JSON formats instantly

What is YAML ↔ JSON?

YAML (YAML Ain't Markup Language) and JSON (JavaScript Object Notation) are both data serialization formats used extensively in software development, but they serve different ergonomic niches. JSON's strict, minimal syntax makes it ideal for machine-to-machine communication — APIs, configuration parsing, and data storage. YAML's indentation-based syntax, support for comments, and multi-line strings make it the preferred choice for human-authored configuration files like Docker Compose, Kubernetes manifests, GitHub Actions workflows, and Ansible playbooks.

Despite representing the same data model — objects (mappings), arrays (sequences), and scalar values — the two formats are not directly interchangeable in practice. YAML supports features that JSON lacks: comments, anchors and aliases for value reuse, multi-line string blocks, and more flexible type inference. Converting between them requires understanding these differences and knowing what information may be lost or transformed during the process.

A YAML-to-JSON converter is an essential tool in the modern DevOps and cloud-native workflow. Kubernetes APIs accept JSON but configurations are typically authored in YAML. CI/CD pipelines often need to transform between formats. Debugging a YAML parse error is sometimes easier by converting to JSON and seeing the result in a stricter format. The converter handles these conversions accurately and instantly, catching syntax errors along the way.

How it works

YAML parsing is substantially more complex than JSON parsing because YAML's syntax is indentation-sensitive and supports a much wider feature set. The parser (powered by the js-yaml library, a mature JavaScript implementation) reads the input line by line, tracking indentation depth to determine nesting. It identifies mappings (key: value pairs), sequences (items prefixed with -), scalars (strings, numbers, booleans, null), and structural indicators like anchors, aliases, and tags.

After parsing YAML into an in-memory JavaScript object, converting to JSON is straightforward — JSON.stringify() serializes the object with configurable indentation. The reverse direction works similarly: JSON.parse() produces an in-memory object, and the js-yaml library's dump function serializes it back to YAML with configurable style options (block vs. flow, quote style, line width). Both directions validate the input strictly — invalid syntax produces a descriptive error message with the offending line number.

Several edge cases require careful handling during conversion. YAML comments are discarded when converting to JSON because JSON has no comment syntax. Anchors and aliases are resolved to their concrete values. YAML's type inference (where unquoted "true" becomes a boolean and "123" becomes a number) may not match the user's intent, which is why the tool displays the parsed types clearly so you can verify the result. Multi-line strings are converted to single-line JSON strings with escaped newline characters.

How to use this tool

  1. Paste YAML content in the left panel to convert to JSON, or paste JSON content to convert to YAML. The tool auto-detects the input format based on syntax.
  2. Click the convert button (or watch automatic conversion happen as you type) to see the output in the opposite format in the right panel.
  3. If the input contains syntax errors, an error message will indicate the line number and nature of the problem — common issues include inconsistent indentation in YAML or trailing commas in JSON.
  4. Review the output carefully, especially for values that YAML infers as non-string types. Unquoted values like "yes," "no," "null," and bare numbers may be converted to booleans, null, or numeric types rather than strings.
  5. Copy the converted output for use in your project. When converting YAML to JSON for API consumption, the output is valid JSON ready for programmatic use.

Examples

Converting a Docker Compose file to JSON

Docker Compose files are authored in YAML, but some tools and APIs accept only JSON. Paste the docker-compose.yml content to get a JSON equivalent with proper nesting of services, networks, volumes, and their configuration options. Comments in the YAML source will be stripped since JSON does not support them.

Converting a Kubernetes manifest for API debugging

Kubernetes resources are typically written in YAML but the API server accepts and returns JSON. Converting a deployment manifest to JSON lets you compare it directly against API responses when debugging issues like why a pod spec does not match what you defined.

Transforming a JSON API response into readable YAML

Take a dense JSON response from a REST API — say, a cloud provider's resource description — and convert it to YAML for a more readable view. YAML's indentation-based nesting and lack of curly braces make deeply nested structures easier to scan, especially for configuration review or documentation purposes.

Validating YAML syntax through round-trip conversion

If you suspect a YAML file has a subtle syntax error (like a tab mixed with spaces or an unquoted string that parses as a boolean), convert it to JSON and inspect the result. Unexpected types or missing values in the JSON output reveal YAML parsing issues that might not produce explicit errors but silently yield wrong data.

About this tool

Paste YAML to get JSON or paste JSON to get YAML — bidirectional conversion with validation and error reporting. Uses the js-yaml library for accurate parsing and serialization.

Common use cases

  • • Converting Kubernetes manifests or Docker Compose files from YAML to JSON for API consumption
  • • Transforming JSON API responses to YAML for easier reading and editing
  • • Migrating configuration files between formats when switching tools or platforms
  • • Validating YAML syntax by attempting a round-trip conversion to JSON and back

Frequently asked questions

Is the conversion lossless?
Yes, for data content. Both YAML and JSON represent the same data types (objects, arrays, strings, numbers, booleans, null). However, YAML comments are lost when converting to JSON since JSON does not support comments.
Which YAML features are supported?
The converter supports YAML 1.2 including multi-line strings (literal and folded), anchors and aliases, nested structures, and all standard data types. It uses the js-yaml library for accurate parsing.
Can I convert multi-document YAML files?
The tool processes single YAML documents. If your file contains multiple documents separated by ---, paste each document separately for conversion.
How are YAML anchors and aliases handled during conversion?
Anchors (&name) and aliases (*name) are a YAML-specific feature for reusing values. During conversion to JSON, anchors are resolved — each alias is replaced with the actual value it references, producing self-contained JSON without any reference mechanism. Converting back to YAML will not recreate the anchors since the alias relationship is not preserved in JSON.
Why does my YAML number get converted to a different type in JSON?
YAML's type inference can be surprising. Values like 0755 are interpreted as octal numbers (493 in decimal) in YAML 1.1, and bare words like yes, no, on, off are parsed as booleans. YAML 1.2 (used by this tool) is stricter but still infers types from unquoted values. If a value converts unexpectedly, wrap it in quotes in the YAML source to force it to be treated as a string.
What happens to YAML multi-line strings in JSON?
YAML supports literal (|) and folded (>) multi-line string styles. During conversion, literal blocks preserve newlines as \n characters in the JSON string, while folded blocks replace single newlines with spaces (and preserve double newlines as paragraph breaks). The resulting JSON string is a single-line value with embedded escape sequences representing the original line breaks.