YAML Validator & Formatter | Free Tool

Table of Contents(11 sections)

How to Use This Tool
The #1 YAML Mistake: Tabs vs Spaces
How to Fix Tab Issues
Common YAML Errors
1. Inconsistent Indentation
2. Missing Space After Colon
3. Unquoted Special Values
4. Nested Quote Escaping
Games & Plugins That Use YAML
YAML Syntax Quick Reference
Valid YAML Structure

Input

Validate as I type

Supported extensions: .yml, .yaml

How to Use This Tool

Paste your YAML into the input area above
Click Validate & Format to check for errors
If valid, the formatted output appears with consistent indentation
Copy or download the cleaned-up YAML file

Enable “Validate as I type” for real-time feedback while editing.

The #1 YAML Mistake: Tabs vs Spaces

YAML Does Not Allow Tabs

This is the most common YAML error. YAML strictly forbids tab characters for indentation. You must use spaces only. Many text editors insert tabs by default — this breaks YAML files silently.

# ❌ WRONG - using tabs (invisible but breaks everything)
settings:
	enabled: true    # Tab character here!
	max-players: 20

# ✅ CORRECT - using spaces
settings:
  enabled: true      # 2 spaces
  max-players: 20

How to Fix Tab Issues

In VS Code: Enable “Render Whitespace” to see tabs vs spaces
Find & Replace: Search for \t and replace with spaces
Editor Settings: Set your editor to insert spaces when you press Tab

Common YAML Errors

1. Inconsistent Indentation

All items at the same level must have identical indentation:

# ❌ WRONG - mixed indentation (2 and 4 spaces)
settings:
  enabled: true
    max-players: 20    # 4 spaces - wrong!

# ✅ CORRECT - consistent indentation
settings:
  enabled: true        # 2 spaces
  max-players: 20      # 2 spaces

2. Missing Space After Colon

YAML requires a space after the colon in key-value pairs:

# ❌ WRONG - no space after colon
name:MyServer
port:25565

# ✅ CORRECT - space after colon
name: MyServer
port: 25565

3. Unquoted Special Values

Some values need quotes to be interpreted correctly:

# ❌ WRONG - these get misinterpreted
version: 1.20        # Becomes float 1.2
enabled: yes         # Becomes boolean true
password: @secret    # @ is special character

# ✅ CORRECT - use quotes
version: "1.20"      # String "1.20"
enabled: "yes"       # String "yes"
password: "@secret"  # String "@secret"

4. Nested Quote Escaping

Be careful with quotes inside strings:

# ❌ WRONG - unescaped quotes
message: Click the "download" button

# ✅ CORRECT - escape or use different quotes
message: 'Click the "download" button'
message: "Click the \"download\" button"

Games & Plugins That Use YAML

Game/Plugin	Config Files	Common Issues
Spigot/Paper	`spigot.yml`, `paper.yml`	Nested structure complexity
Essentials	`config.yml`, `worth.yml`	Deep nesting, special characters
LuckPerms	`config.yml`	Permission node formatting
WorldEdit	`config.yml`	Path formatting
WorldGuard	`config.yml`, region files	Flag values
Vault	Various plugin configs	Cross-plugin compatibility

Minecraft Server Admins

After editing any YAML config, always validate before restarting your server. A single misplaced space can prevent your plugins from loading.

YAML Syntax Quick Reference

Element	Syntax	Example
Strings	Usually no quotes	`name: My Server`
Numbers	No quotes	`port: 25565`
Booleans	`true`/`false`	`enabled: true`
Null	`null` or `~`	`value: null`
Lists	Dash prefix	`- item1` `- item2`
Inline Lists	Brackets	`items: [a, b, c]`
Comments	Hash prefix	`# This is a comment`

Valid YAML Structure

# Server configuration
server:
  name: My Minecraft Server
  port: 25565

settings:
  max-players: 20
  whitelist: true
  motd: "Welcome to the server!"

# List of admin users
admins:
  - PlayerOne
  - PlayerTwo

# Nested configuration
worlds:
  world:
    difficulty: normal
    spawn-monsters: true
  world_nether:
    difficulty: hard

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Frequently Asked Questions

Why can't I use tabs in YAML files?

YAML strictly forbids tab characters for indentation — this is part of the YAML specification, not just a convention. Use spaces only, with 2 or 4 spaces per indentation level recommended. Many text editors insert tabs by default, which breaks YAML files.

How do I fix 'found character that cannot start any token'?

This error usually means there's a tab character, special character that needs quoting, or an unexpected symbol. First, replace all tabs with spaces. Then check for special characters like @, *, or & at the start of values — these need to be wrapped in quotes.

What's the difference between YAML and YML?

Nothing — they're exactly the same format. YML is simply a shorter file extension. Both .yaml and .yml files use identical syntax. Most Minecraft plugins use .yml for brevity.

Why does my Minecraft plugin config break after editing?

Most likely an indentation error. YAML requires consistent spacing — if you mix 2-space and 4-space indentation, or accidentally use tabs, the file becomes invalid. Use this validator to check before restarting your server.

Do I need quotes around strings in YAML?

Usually no. YAML auto-detects strings. However, you need quotes for: strings starting with special characters (@, *, &), strings that look like numbers or booleans ('true', '123'), and strings containing colons followed by spaces.

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