YAML Validator

YAML Validator - Check YAML Syntax Online

Validate your YAML files instantly with our free online validator. Get clear error messages with line numbers for quick debugging.

Paste YAML content into the editor and validation occurs automatically as you type. Syntax errors are highlighted inline with red underlines and error messages appear below specifying the line number and problem type. Common issues detected include indentation errors, unclosed quotes, invalid keys, duplicate keys, and anchor/alias problems. The validator follows the YAML 1.2 specification and handles multi-document files (separated by ---). Valid YAML displays a green success message. Validation runs entirely in your browser using a native YAML parser.

Kubernetes engineers validate manifests before applying them to clusters to avoid deployment failures. Ansible users debug playbook syntax errors that cause task execution to halt. CI/CD pipeline developers verify workflow files before committing them to catch configuration mistakes early. Developers working with i18n translation files ensure YAML structure is valid before deploying language updates.

Indentation is the most common error source—use an editor with visible whitespace to catch tab/space mixing. YAML keys must be unique within the same mapping level; duplicate keys often occur when copy-pasting blocks. Unquoted strings starting with special characters (like @, *, &) can trigger parser errors—wrap them in quotes. Multi-line strings have multiple syntaxes (| for literal, > for folded)—choose the right one to preserve or strip newlines. Always validate after editing deeply nested structures where indentation alignment is error-prone.

All processing happens directly in your browser. Your files never leave your device — no server uploads, no cloud storage, no data retention. The tool works offline once loaded, requires no registration, and is completely free with no usage limits.