YAML Validator — Check YAML Syntax Online

#What this tool does

This YAML validator parses your input using js-yaml — the same library used by most Node.js Kubernetes tooling. It catches syntax errors with line and column numbers as you type: tab characters, incorrect indentation, unquoted booleans (yes/no interpreted as true/false), duplicate keys, and malformed sequences.

All validation runs client-side in your browser. Nothing is sent to a server.

#Common YAML pitfalls

# Tab character — invalid YAML
services:
  api:
	replicas: 3
 
# Unquoted boolean — "no" becomes false
deploy: no        # use "no" to keep it a string
 
# Duplicate key — second silently overwrites first
env:
  DATABASE_URL: postgres://prod:5432/app
  DATABASE_URL: postgres://staging:5432/app

#Related tools

Format your YAML with the YAML formatter, or convert between formats with YAML to JSON and JSON to YAML. For API specs, try the OpenAPI validator.

#Open source

This tool is powered by @azin-tech/mini-tools, an open-source developer toolkit. View source on GitHub.