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OpenAPI Validator

Check an OpenAPI 3.x specification — written in either JSON or YAML — against the structure the spec requires: the version field, Info Object, path items and operations, parameter rules, response shapes, and internal $ref resolution. Problems are split into errors and warnings and reported at the exact location in the document, and your specification is never modified.

OpenAPI 3.x — JSON or YAML, auto-detected

Paste an OpenAPI 3.x document to validate it.

This checks the document’s structure against the OpenAPI 3.x specification — required fields, object shapes, response and parameter rules, duplicate operationIds, path-template/parameter mismatches, and internal $ref resolution. It is not a full JSON Schema validation of the OpenAPI meta-schema, and external $refs are reported rather than fetched. Your document is never modified — the normalised output below is just the same document re-printed as JSON.

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Related tools

YAML ValidatorCheck whether YAML is valid, with a precise error location.JSON ValidatorCheck whether JSON is valid, with a precise error location.API TesterSend HTTP requests and inspect the status, headers, and response body.

Features

  • JSON and YAML, detected automatically
  • Errors and warnings separated, each located by document path
  • Internal $ref resolution and duplicate operationId detection
  • Path-template parameters checked against declared parameters
  • Normalised JSON output — your document is never altered

How to use

  1. Paste your OpenAPI 3.x document in JSON or YAML.
  2. Review the errors and warnings listed by path.
  3. Fix the document in your own editor and re-paste to confirm.

FAQ

What exactly does this check?
The document's structure against the OpenAPI 3.x specification: the openapi version field, required Info fields, Paths and Path Item shapes, operation responses, parameter rules, component key format, duplicate operationIds, path-template/parameter mismatches, and whether every internal $ref resolves. It is not a full JSON Schema validation of the OpenAPI meta-schema, and it says so rather than implying more coverage than it has.
What's the difference between an error and a warning?
An error means the document violates the specification and conforming tooling will reject it. A warning means it's legal but likely a problem in practice — a missing operationId, no servers block, or no success response declared.
Does it support Swagger 2.0?
No. A Swagger 2.0 document is detected and reported as such so you know to convert it, rather than being validated against rules that don't apply to it.
Are external $refs followed?
No. Fetching arbitrary URLs from the browser would be blocked by CORS anyway, so external references are reported as unresolved-by-design rather than silently treated as valid.