OpenAPI Validator

This tool targets OpenAPI 3.x (3.0.x and 3.1.x). It validates required fields, checks for structural issues, and reports common mistakes in OpenAPI 3 specs. It accepts both YAML and JSON format.

It checks for required fields (openapi, info.title, info.version), validates all paths start with /, detects duplicate paths, finds missing operationIds, flags operations without responses, checks path parameter definitions, and warns about missing descriptions and server definitions.

Yes — you can paste YAML or JSON. The built-in parser handles standard OpenAPI YAML structures including nested objects and arrays. Very complex YAML (anchors, aliases, multi-line strings) may need to be converted to JSON first.

An operationId is a unique string identifying each API operation. It's required by many API client generators (like openapi-generator) and documentation tools. Missing or duplicate operationIds will cause issues when generating SDKs or documentation.

No — all validation runs entirely in your browser using JavaScript. Your OpenAPI spec never leaves your machine.

Errors are issues that violate the OpenAPI specification and will likely cause problems with tooling (missing required fields, duplicate operationIds, undefined path parameters). Warnings are best-practice issues that won't break things but may cause poor documentation or SDK generation. Info items are suggestions for improvement.