YAML Validator

How to Use

1. Paste your YAML content into the text area.
2. Click Validate (or press Ctrl+Enter).
3. If the YAML is valid, a green success message appears and the parsed structure is shown as JSON below.
4. If the YAML is invalid, an error box shows the reason, line number, and column — plus a snippet of the offending area.

Understanding the Error Output

When validation fails, the error box contains:

• Reason — a plain-English description of what went wrong (e.g., bad indentation, unexpected end of stream).
• Line & Column — the exact position of the error in your input.
• Snippet — the surrounding context from the parser, often showing a caret (^) pointing at the problem character.

Common YAML Syntax Errors

• Inconsistent indentation — YAML requires consistent use of spaces (never tabs) for nesting. Mixing 2-space and 4-space indentation on the same level causes parse errors.
• Missing colon after a key — key value is invalid; it must be key: value.
• Unquoted special characters — characters like :, #, [, ], {, } in values must be quoted or escaped.
• Tab characters — YAML prohibits tabs for indentation. Replace all tabs with spaces.
• Duplicate keys — while some parsers allow them, duplicate keys in the same mapping block are technically invalid YAML 1.2.

Example: Valid YAML

server:
  host: localhost
  port: 8080
  tls: true

database:
  driver: postgres
  name: myapp
  credentials:
    user: admin
    password: "s3cr3t"

allowed_origins:
  - https://example.com
  - https://api.example.com

Example: Invalid YAML (indentation error)

server:
  host: localhost
   port: 8080   # error: extra space causes inconsistent indentation

The validator will report the line and column where the inconsistency is detected, making it easy to locate and fix.