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YAML Formatter & Validator

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About YAML Formatter & Validator

The YAML Formatter and Validator is a free online tool that formats, validates, and converts YAML documents. Paste your YAML and instantly check it for syntax errors, reformat it with consistent indentation, or convert it to JSON for use in systems that do not accept YAML directly.

YAML (YAML Ain't Markup Language) is the configuration standard for Docker Compose files, Kubernetes manifests, GitHub Actions workflows, Ansible playbooks, Helm charts, CircleCI pipelines, AWS CloudFormation (in YAML mode), and many application config frameworks. A single indentation error can break an entire deployment or pipeline run, making a validator an essential tool in any DevOps or configuration workflow.

The formatter normalizes indentation to a consistent style (2-space by default, configurable), sorts keys alphabetically when requested, and removes trailing whitespace. The validator reports the exact line and column of any syntax error — misaligned indentation, invalid characters in keys, or unclosed block scalars.

The JSON conversion mode is particularly useful when an API, tool, or platform requires JSON but your source configuration is maintained as YAML. The converter handles nested objects, arrays, multi-line strings, anchors, and aliases.

All processing runs locally in your browser. Your YAML content is never uploaded or stored.

How to Use YAML Formatter & Validator

  1. Paste your YAML into the input.

  2. Choose Format (normalize indentation) or Convert to JSON.

  3. Errors are highlighted with line numbers.

  4. Copy the formatted or converted result.

Examples

Example — YAML → JSON
Input
name: Alice
age: 30
active: true
Output
{"name":"Alice","age":30,"active":true}

Frequently Asked Questions

Can it convert YAML to JSON?

Yes — use YAML → JSON mode to convert any valid YAML document to its JSON equivalent.

Why does YAML not allow tabs?

The YAML specification forbids tab characters for indentation. Only spaces are valid. This is a common source of errors when editing YAML in certain text editors.

What is the difference between YAML and JSON?

YAML is a superset of JSON and is designed for human readability. It supports comments, multi-line strings, anchors and aliases, and does not require quotes for strings in most cases.

Can I use this for Kubernetes manifests?

Yes — Kubernetes YAML files follow standard YAML syntax. Paste your manifest to validate it and check for indentation errors before applying it.

Does it support YAML anchors and aliases?

Yes — YAML anchors (&name) and aliases (*name) are parsed and resolved correctly.