OpenAPI Validator
LiveValidate OpenAPI 3.x and Swagger 2.0 YAML/JSON specs and report all structural errors.
Understanding OpenAPI / Swagger Specification
OpenAPI specifications serve as the single source of truth for API contracts between teams, tools, and consumers. An invalid or incomplete OpenAPI spec breaks code generators, documentation tools, API gateways, and contract testing frameworks. Common errors include missing required fields like operationId, invalid $ref paths that do not resolve, parameters referenced in paths but not defined in the parameters array, and schema type mismatches. Catching these locally before committing saves review cycles and CI failures.
Paste an OpenAPI 3.0 or Swagger 2.0 specification in YAML or JSON and validate it against the schema rules. Reports missing required fields, invalid types, malformed $ref references, missing operationIds, duplicate paths, and parameter errors — all with their locations in the document. 100% client-side validation using ajv.
The Devkitr OpenAPI Validator parses OpenAPI 3.0.x and Swagger 2.0 specs in YAML or JSON format and reports all structural, reference, and schema validation errors with their locations in the document.
In a typical development workflow, OpenAPI Validator becomes valuable whenever you need to validate openapi 3. Whether you are working on a personal side project, maintaining production applications for a company, or collaborating with a distributed team across time zones, having a reliable browser-based validation tool eliminates the need to install desktop software, write one-off scripts, or send data to third-party services that may log or retain your information. Since OpenAPI Validator processes everything locally on your device, your data stays private and your workflow stays uninterrupted — open a browser tab, paste your input, get your result.
Key Features
OpenAPI 3.0 & Swagger 2.0
Validates both OpenAPI 3.0.x (JSON and YAML) and Swagger 2.0 (JSON and YAML) specification formats.
Structural Validation
Checks required fields, valid data types, correct response structures, and parameter definitions against the official JSON Schema for OpenAPI.
Detailed Error Reports
Reports each error with its location path in the document (e.g., paths./users.get.parameters[0]) and a description of the violation.
YAML and JSON Input
Accepts both YAML and JSON formatted specs — auto-detects the format.
How to Use OpenAPI Validator
Paste Spec
Paste your OpenAPI 3.0 or Swagger 2.0 specification in YAML or JSON format.
Validate
Click Validate to run the structural and schema validation.
Review Errors
Read each error report with its location path and fix the corresponding issues in your spec.
Iterate
Re-paste the fixed spec and validate again until all errors are resolved.
Use Cases
Pre-commit Validation
Validate the spec locally before committing to catch errors before CI runs code generators or documentation builds against it.
API Design Review
Verify a spec is structurally valid before distributing it to consumers for review — avoids wasting reviewer time on spec errors.
Code Generator Preparation
Code generators (openapi-generator, swagger-codegen) fail or produce broken code from invalid specs. Validate first to ensure clean generation.
Contract Testing Setup
Contract testing tools require a valid spec — validate before configuring Pact, Dredd, or other contract testing frameworks.
Pro Tips
operationId is technically optional in OpenAPI but most tooling (code generators, documentation, clients) requires it. Always include unique operationId values for every operation.
Use $ref for reusable schemas in components/schemas rather than duplicating schema definitions — it reduces maintenance overhead and keeps specs DRY.
Common Pitfalls
Defining path parameters in the path string (/users/{id}) without declaring them in the operation's parameters array
Fix: Every path parameter must be declared in the parameters array with in: path, required: true, and a schema definition for the validator and code generators to use it correctly.
Frequently Asked Questions
QWhich versions are supported?
OpenAPI 3.0.x and Swagger 2.0 YAML and JSON formats are both supported.
QWhat errors does it detect?
Missing required fields, invalid types, bad $ref paths, duplicate operation IDs, missing path parameters, and malformed schema definitions.
QIs my spec sent to a server?
No. All validation runs in your browser using a bundled JSON Schema validator. Your API spec never leaves your device.
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