YAML Validator & Linter: Validate YAML Syntax Online

Validate YAML files with line and column error reporting. Convert YAML to formatted JSON and JSON back to YAML seamlessly without server transmission.

Valid YAML Document

YAML Input2 spaces per indent

JSON OutputReal-time parsed

{
  "version": "3.8",
  "services": {
    "web": {
      "image": "nginx:alpine",
      "ports": [
        "80:80"
      ],
      "environment": [
        "NODE_ENV=production"
      ],
      "restart": "always"
    },
    "database": {
      "image": "postgres:15",
      "volumes": [
        "db_data:/var/lib/postgresql/data"
      ]
    }
  },
  "volumes": {
    "db_data": null
  }
}

How to Use YAML Validator & Linter

Type or paste your YAML configuration or manifest into the left editor.
View instantaneous validation: clean YAML displays a green "Valid YAML" badge; syntax errors show exact lines and columns.
View the converted JSON representation side-by-side in real-time.
Convert back and forth between YAML and JSON with one click.

Practical Examples

Docker Compose YAML to JSON

Parses arrays, environment strings, and nested maps.

Input:

services:
  app:
    image: node:20

Output:

{
  "services": {
    "app": {
      "image": "node:20"
    }
  }
}

Common Mistakes & Troubleshooting

Using tab characters instead of spaces: the YAML specification strictly forbids tab indentation! Use 2 spaces per indentation level.
Duplicate keys at the same indentation level: YAML parsers will error on duplicate map keys.

Frequently Asked Questions

Why does YAML forbid tab indentation?

The YAML specification strictly disallows tab characters for indentation because different text editors and operating systems render tabs with differing visual widths (e.g. 2, 4, or 8 columns), making nested hierarchies ambiguous. Always use 2 or 4 spaces.

How does YAML indentation hierarchy work?

YAML uses whitespace indentation to define scope and relationships. Child elements must be indented deeper than their parent element. Items in a sequence are designated by a leading dash followed by a space (- item).

Can I validate Kubernetes manifests and Docker Compose files?

Yes! FormatFlow supports multi-document YAML syntax, configuration maps, environment arrays, and complex deployment manifests with instant client-side linting.

Does this validator support anchors and aliases?

Yes! FormatFlow uses the full-spec js-yaml parser which completely resolves YAML anchors (&anchor) and aliases (*anchor).