OpenAPI & Swagger Validator for JSON or YAML
About OpenAPI Validator
The OpenAPI and Swagger Validator checks the core structure of an API description written in JSON or YAML. It recognizes OpenAPI 3.x and Swagger 2.0 version fields, verifies required info and paths structures, inspects HTTP operations and confirms that each operation declares at least one response.
The report summarizes paths and operations, lists errors and warnings with document paths, and includes an operation inventory that is useful during review. Local $ref values are resolved as JSON Pointers; unresolved pointers are errors, while external references are identified as warnings because this browser-only checker does not fetch them.
This is a fast structural preflight, not a replacement for a complete specification validator or API contract test suite. It does not implement every semantic rule in the OpenAPI standards, download external documents or call described endpoints. Run a full validator in CI when publication depends on exhaustive conformance.
How it works
Parse either JSON or YAML
The input is attempted as JSON first and then YAML. Parsing happens locally, so private server URLs, schema names and examples are not sent to a validation service.
Check the document and operation structure
The validator checks the version marker, info title and version, the paths object, leading slashes on route templates, operation objects and response maps. Duplicate operationId values are reported as errors.
Resolve internal component references
Local references beginning with #/ are decoded according to JSON Pointer escaping and followed within the same document. Turn the reference check off when you only need an operation overview.
Separate errors from review warnings
Missing required structures and broken local references make the report invalid. Optional operationId checks and unfetched external references appear as warnings so you can distinguish a structural failure from a review item.
Frequently asked questions
Which API description versions can I check?
The structural checks target OpenAPI 3.0, OpenAPI 3.1 and Swagger 2.0 documents. Other declared versions receive a warning and still receive the generic structural checks.
Does this fully validate the OpenAPI specification?
No. It is a focused structural validator for required top-level data, operations, responses, operationId uniqueness and local references. Use a complete standards validator in CI for exhaustive rules.
Are external $ref documents downloaded?
No. External references are listed as warnings and are not fetched. This keeps processing local and avoids unexpected network access.
Does the validator send requests to my API?
No. It only reads the description document. It does not contact servers, execute operations or verify that live responses match the schemas.