YAML Formatter & Validator - Format YAML Online

Free YAML formatter and validator. Format, validate and convert YAML files directly in your browser.

Paste your YAML here...

More Tools

JSON Formatter|Regex Tester|Base64|UUID Generator

What is YAML?

YAML (YAML Ain't Markup Language) is a human-readable data serialization language. It is commonly used for configuration files, data exchange between languages, and in applications where data is being stored or transmitted. YAML's syntax is designed to be easy to read and write, using indentation to represent data structure, making it popular in DevOps, CI/CD pipelines (GitHub Actions, GitLab CI), Docker Compose, Kubernetes, and Ansible.

YAML vs JSON

Both YAML and JSON are data serialization formats, but they serve different purposes. YAML prioritizes human readability with a minimal syntax using indentation — it supports comments, anchors, and complex data types. JSON is more machine-oriented with strict syntax using braces and brackets — it's the standard for web APIs and has faster parsing. YAML is a superset of JSON, meaning any valid JSON is also valid YAML. Our tool lets you convert between both formats seamlessly.

YAML Examples

Basic YAML

name: John Doe
age: 30
active: true
skills:
  - Python
  - JavaScript
  - DevOps

Docker Compose

version: '3.8'
services:
  web:
    image: nginx:latest
    ports:
      - 8080:80
    volumes:
      - ./app:/usr/share/nginx/html

YAML Syntax Guide

Key-Value Pairs

Basic structure: key: value. Strings do not require quotes unless they contain special characters.

Lists

Use - prefix for list items. Each item can be any YAML type including nested objects.

Nested Objects

Use indentation (2 or 4 spaces) to represent nested structures. Consistent indentation is required.

Comments

Use # for comments. YAML supports inline and block comments.

How to Use YAML Formatter

  1. 1

    Paste your YAML content into the input editor

  2. 2

    Click "Format" to beautify or "Validate" to check for errors

  3. 3

    Use "YAML to JSON" or "JSON to YAML" to convert between formats

  4. 4

    Copy the formatted output or download it as a file

Frequently Asked Questions

What is YAML used for?

YAML is primarily used for configuration files in software development and DevOps. Common use cases include Docker Compose files, Kubernetes manifests, CI/CD pipeline definitions (GitHub Actions, GitLab CI), Ansible playbooks, and application configuration. YAML's readability makes it ideal for files that developers and operators need to read and edit manually.

Is it safe to validate YAML online?

Yes. Our YAML validator runs entirely in your browser using JavaScript. Your YAML data never leaves your device — we do not upload, store, or share any data. All parsing, validation, and conversion happens locally on your machine.

Can YAML be converted to JSON?

Yes. YAML is a superset of JSON, meaning any JSON document is valid YAML, and most YAML can be converted to JSON. Our tool provides one-click conversion between YAML and JSON in both directions. Note that some YAML-specific features like anchors and aliases may not have a direct JSON equivalent.

What are common YAML errors?

Common YAML errors include: inconsistent indentation (mixing tabs and spaces), using tabs instead of spaces, missing colons after keys, incorrect list formatting, and unquoted strings that look like other YAML types (like 'true', 'false', 'null', or numbers). Our validator catches these errors and shows you exactly where they occur.