Real-time validation of OpenAPI/Swagger document structure, field completeness, and reference validity with precise error location
Zero Dependencies · Works OfflineThe OpenAPI Validator is a free online developer tool that performs real-time validation of OpenAPI/Swagger API document specification compliance. It checks required fields, field types, reference path validity, HTTP method legality, status code format, Schema structure, and more, with precise error positioning. Supports OpenAPI 3.0/3.1 and Swagger 2.0 with automatic version detection. Ideal for API developers writing and debugging API documentation to ensure spec compliance. All validation happens locally in your browser — API document content is never uploaded to any server.
1. Paste your OpenAPI/Swagger document content into the input area (supports JSON and YAML formats).
2. Click "Validate" or press Ctrl+Enter to analyze the document immediately.
3. Review results: statistics show error/warning counts, detailed list shows issue locations.
4. Fix errors based on the messages, then re-validate until all checks pass.
5. Click "Copy Report" or "Download Report" to save validation results.
API developers validate spec compliance in real-time while writing OpenAPI docs, reducing errors and improving documentation quality.
Teams use this tool to quickly check document spec compliance during API design reviews, ensuring design consistency.
DevOps engineers validate OpenAPI document format before configuring API gateways (Kong, AWS API Gateway), avoiding import failures.
The OpenAPI Specification (OAS, formerly Swagger Specification) is the REST API description standard, with current mainstream versions being 3.0.x and 3.1.x. OpenAPI 3.0 is based on JSON Schema draft-04, while 3.1 uses draft-2020-12. Core structure includes: openapi (version), info (metadata), servers (server list), paths (API paths), components (reusable components), security (security schemes), and tags (tag grouping). $ref references avoid duplicate definitions, formatted as #/components/schemas/XXX. Swagger 2.0 is the legacy spec with a slightly different structure (swagger field, definitions instead of components).
Yes. Supports OpenAPI 3.0.x, 3.1.x, and Swagger 2.0 with auto-detection and corresponding rules.
Required fields, field types, reference validity, HTTP methods, status codes, Schema structure, server URLs, and security scheme references.
This tool provides basic structural validation for quick pre-checks. Spectral offers richer custom rules for CI/CD. Use both together.
Yes. All validation happens locally in your browser. API document content is never uploaded.
Yes. Auto-detects input format without manual specification.
Yes. Drag .yaml/.yml/.json files onto the input area to auto-load content.
The tool checks if $ref paths point to existing definitions in the document, e.g., #/components/schemas/User must have User defined in components.schemas.