Free YAML Validator – Check YAML Syntax Online

Validate YAML syntax instantly. Catch errors, warnings, and formatting issues. Detailed line-by-line feedback. Free, fast, and browser-based.

What Is YAML Validation?

YAML validation checks your YAML content for syntax errors, structural issues, and formatting problems. Valid YAML can be parsed by applications; invalid YAML causes configuration failures and runtime errors.

Why Validate YAML?

Prevent Errors: Catch syntax issues before deployment or runtime.

Configuration Safety: Ensure config files parse correctly.

Debug Quickly: Identify exact line numbers with problems.

Best Practices: Get warnings for non-standard formatting.

How to Use This Tool

Step 1: Paste YAML

Enter your YAML configuration or data.

Step 2: View Results

See validation status with errors and warnings.

Step 3: Fix Issues

Use line numbers to locate and fix problems.

What Gets Validated

Errors (Invalid YAML)

Issue	Example	Resolution
Tab indentation	`key: value`	Use spaces only
Missing space after colon	`key:value`	Add space: `key: value`
Unclosed quotes	`name: "value`	Close the quote
Missing list space	`-item`	Add space: `- item`

Warnings (Valid but Problematic)

Issue	Description
Trailing whitespace	Spaces at line end
Odd indentation	Non-standard indent levels
Special characters in keys	Unquoted special chars
Duplicate keys	Same key appears twice

Common YAML Mistakes

Indentation Errors

Wrong (tabs):

app:
	name: test

Right (spaces):

app:
  name: test

Colon Spacing

Wrong:

name:value

Right:

name: value

Quote Handling

Wrong:

message: "Hello World

Right:

message: "Hello World"

YAML Syntax Reference

Basic Structure

# Comment
key: value
number: 123
boolean: true
null_value: null

Nested Objects

parent:
  child1: value1
  child2: value2
  nested:
    deep: value

Lists

items:
  - first
  - second
  - third

inline: [a, b, c]

Multi-line Strings

# Literal (preserves newlines)
literal: |
  Line one
  Line two

# Folded (joins lines)
folded: >
  This becomes
  one line

Frequently Asked Questions

Why can't I use tabs?

YAML specification requires spaces. Tabs cause parsing failures.

What indentation should I use?

2 spaces is standard. Be consistent throughout the file.

Are quotes required?

Only for special characters or when strings look like other types.

Does this check against a schema?

This validates syntax only. Schema validation requires a schema definition.

Related Tools

YAML Formatter — Format YAML
JSON Validator — Validate JSON
JSON to YAML — Convert formats
YAML to JSON — Convert formats

Paste your YAML above to validate. Get instant feedback on errors and warnings.