How do I include special characters in strings?

Quote strings with special characters: colons, hashes, brackets. Single or double quotes work. For multi-line, use | (literal) or > (folded) block scalars.

Why is "yes" becoming true in my YAML?

YAML interprets yes/no, on/off, true/false as booleans. Quote them if you need strings: "yes". This is a common gotcha with country codes (NO for Norway).

Can I validate against a schema?

Yes, JSON Schema works for YAML. Tools like yamllint can check both syntax and schema. Kubernetes has its own schema validation for manifest files.

YAML Validator

Guide & TutorialOffline

Validate and format YAML documents

Validate and format YAML documents instantly with our free online YAML validator. This tool helps developers and DevOps engineers check YAML syntax, identify indentation errors, and beautify YAML files for configuration management. Simply paste your YAML content and get instant validation.

Input YAML

0 characters, 1 lines

Validation Result

About YAML Validation

YAML (YAML Ain't Markup Language) is a human-friendly data serialization format. This validator checks if your YAML is properly formatted according to YAML specifications.

Common errors:

Incorrect indentation (YAML is indentation-sensitive)
Invalid use of tabs (use spaces instead)
Missing colons or improper key-value syntax
Unclosed quotes or brackets
Invalid characters in keys

About YAML Validator

YAML validation ensures configuration files are syntactically correct and properly structured. YAML's indentation-based syntax makes it easy to accidentally break files with wrong spacing or formatting. Validation catches these issues before they cause deployment failures.

How It Works

The validator parses YAML syntax checking: proper indentation (consistent spaces, no tabs), key-value structure, list formatting, multi-line strings, anchors/aliases, and special values. It reports line numbers and specific error descriptions.

Technical Details

YAML is indentation-sensitive - inconsistent spaces break parsing. Key rules: use spaces not tabs, consistent indentation (typically 2 spaces), colon after keys, dash for lists. Special values: null, true/false, numbers vs strings. Multi-document files use --- separators.

Common Use Cases

CI/CD Configuration

Validate GitHub Actions, GitLab CI, etc.

Catch indentation errors in workflow files

Kubernetes Manifests

Validate K8s deployment, service, configmap files.

Docker Compose

Ensure docker-compose.yml is valid.

Application Config

Validate app configuration files.

Code Examples

Common YAML Errors

yaml

# Wrong - tabs instead of spaces
name:	John  # Tab character!

# Wrong - inconsistent indentation
person:
  name: John
   age: 30  # 3 spaces instead of 2

# Wrong - missing space after colon
key:value  # Should be "key: value"

# Correct YAML
person:
  name: John
  age: 30
  active: true
  country: "NO"  # Quoted to avoid boolean

YAML is sensitive to whitespace. Use consistent 2-space indentation and never use tabs.

Tips & Best Practices

Use 2 spaces for indentation, never tabs
Configure editor to show whitespace characters
Quote strings that could be misinterpreted (yes, no, numbers)
Use yamllint for style checking beyond syntax
Validate in CI to catch errors before deployment

Common Mistakes to Avoid

Using tabs instead of spaces
Inconsistent indentation levels
Missing space after colon
Unquoted strings being interpreted as other types

When to Use This Tool

Validate YAML for all configuration files: CI/CD pipelines, Kubernetes, Docker Compose, application configs. Essential before deployment to prevent configuration failures.

Frequently Asked Questions

YAML requires consistent indentation. Mix of tabs/spaces, inconsistent indent levels, or wrong alignment causes failures. Use exactly 2 spaces per level, never tabs.

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# Wrong - tabs instead of spaces name: John # Tab character! # Wrong - inconsistent indentation person: name: John age: 30 # 3 spaces instead of 2 # Wrong - missing space after colon key:value # Should be "key: value" # Correct YAML person: name: John age: 30 active: true country: "NO" # Quoted to avoid boolean