Does validation call remote APIs?

No — @apidevtools/swagger-parser runs locally in your browser for this tool.

Are warnings always shown?

The parser reports spec errors; additional style warnings may be empty when none apply.

Runs in browser

Validate OpenAPI 3.x and Swagger 2.0 specs instantly.

Validate OpenAPI 3.x and Swagger 2.0 specs in YAML or JSON. See valid/invalid status, errors, endpoint and schema counts — all in the browser.

OpenAPI (YAML or JSON)

Files never leave your browser.

Drag and drop a file here, or tap to select

Validation

Enter an OpenAPI document to validate.

🔒 Runs in your browser · No uploads · Your data never leaves your device

Paste spec
Load OpenAPI YAML or JSON in the left panel or drop a file.
Review results
Valid specs show a green badge and stats; invalid specs list parser or schema errors.
Chain output
Send a valid document to YAML→JSON or JSON formatter from the tool chain menu.

Validating API specs before publishing — Check an OpenAPI spec for errors and schema violations before publishing to a developer portal or sharing with consumers.
Debugging spec parse errors — Identify which line of an OpenAPI document is causing tooling (code generators, Postman) to reject the file.
Verifying spec changes during refactoring — Validate a modified OpenAPI spec after renaming paths or updating schemas to catch breaking mistakes.

Does validation call remote APIs?: No — @apidevtools/swagger-parser runs locally in your browser for this tool.
Are warnings always shown?: The parser reports spec errors; additional style warnings may be empty when none apply.

OpenAPI: A standard specification format for describing REST APIs, defining endpoints, parameters, request bodies, and responses.
Swagger: The original name for OpenAPI; Swagger 2.0 evolved into OpenAPI 3.0. Tools often support both terms.
Schema object: A JSON Schema-like definition in an OpenAPI spec that describes the shape of request or response data.

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