OpenAPI / Swagger Editor & Validator

About the OpenAPI / Swagger Editor & Validator

Paste or open an OpenAPI 3.0, 3.1 or 3.2 document — or a Swagger 2.0 one — in YAML or JSON. It is checked as you type against the official JSON Schema of its version from spec.openapis.org, plus the rules a schema cannot express: references that point nowhere, duplicate operationIds, path parameters missing from the path (or the path template missing a parameter), duplicate parameters, paths that differ only in parameter names, unknown security schemes and scopes, server variables, required properties that do not exist and more. Every problem has its line, and a click selects it in the editor.

The Reference view renders the API: operations grouped by tag with parameters, request bodies, responses and schema trees, an example payload generated from each schema, and a ready-to-run curl command. Convert turns YAML into JSON and back, and upgrades Swagger 2.0 or OpenAPI 3.0 to OpenAPI 3.1. Everything happens in your browser.

Common uses

• Checking an API description before publishing it, or in review, without installing a linter.
• Reading an unfamiliar API: what each operation takes and returns, with example payloads.
• Getting a curl command for an endpoint to try it from a terminal (or paste it into the REST API Tester).
• Moving an old Swagger 2.0 description to OpenAPI 3.1.

What is checked

• Syntax: YAML or JSON errors with the exact position; duplicate keys; a document that is not one mapping.
• The version: openapi: 3.1 written without quotes or a patch number is read as a number, which is the most common reason a document “has no version”.
• The official schema of the version: Swagger 2.0 (2017-08-27), OpenAPI 3.0 (2024-10-18), 3.1 (2026-08-03) and 3.2 (2026-08-30), the current editions on spec.openapis.org. Swagger 2.0 parameters are checked against the schema for their in, so a query parameter is not reported as a broken body parameter.
• Rules beyond the schema: local $refs that resolve to nothing (with a “did you mean”), unique operationIds, path templates and their in: path parameters (which must be required: true), duplicate parameters, paths such as /users/{id} and /users/{name} that a server cannot tell apart, security requirements naming undefined schemes or OAuth scopes, server URL variables and their enums, required properties that do not exist, discriminator mappings, examples of the wrong type, nullable in 3.1 (where it is ignored), request bodies on GET and HEAD, and Swagger 2.0’s one-body-parameter rule.
• Notes: schemas, parameters, responses and request bodies that nothing uses; tags that are used but not described.

Examples and curl commands

Each schema gets an example built from its example, examples, default or enum, otherwise from its type: date-time, email, UUID and other formats get realistic values, numbers respect minimum, maximum and multipleOf, allOf parts are merged and readOnly properties are left out of requests (writeOnly ones out of responses). The curl command uses the first server (with its variables’ defaults), example values for path and query parameters, the operation’s security as shell variables such as $TOKEN or $API_KEY, and a JSON, form or multipart body. Parameters the description gives no example for stay as {placeholders}.

Upgrading to OpenAPI 3.1

Swagger 2.0: host, basePath and schemes become servers; definitions, reusable parameters and responses and securityDefinitions move into components (basic auth becomes HTTP basic, OAuth flows are renamed: application → clientCredentials, accessCode → authorizationCode); body and formData parameters become a requestBody with the consumes media types; response schemas and examples move into content with the produces types; parameter types move into schema, and collectionFormat becomes style / explode. OpenAPI 3.0: nullable becomes a "null" type, boolean exclusiveMinimum / exclusiveMaximum become numbers, and example in schemas becomes examples. Key order and number literals are kept exactly. The notes list what needs a human decision.

Limitations

• References to other files or URLs ($ref: ./schemas/pet.yaml) are not loaded; they are listed, and only references inside the document are resolved.
• In OpenAPI 3.1 and 3.2, the official schema leaves Schema Objects open (any JSON Schema dialect is allowed), so keywords inside schemas are only checked by the rules listed above.
• Descriptions are shown as plain text; Markdown formatting is not rendered.
• Requests are not sent from this page — copy the curl command, or use the REST API Tester.
• Upgrading to 3.2 is not offered: 3.1 documents are valid starting points for 3.2 tooling.

Privacy

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.