OpenAPI Generator

Build an OpenAPI 3.0 specification visually and export as YAML or JSON.

Free & unlimited

API information

Title

Version

Base URL

Description

Authentication

Endpoints (1)

get/api/resource1 resp.

Method

Path

Summary

Parameters

Responses

Preview

openapi: '3.0.3'
info:
  title: 'My API'
  version: '1.0.0'
servers:
  - url: 'https://api.example.com'
paths:
  /api/resource:
    get:
      responses:
        200:
          description: 'Successful response'
          content:
            application/json:
              schema:
                type: 'object'
              example:
                id: 1
components:
  securitySchemes:
    BearerAuth:
      type: 'http'
      scheme: 'bearer'
      bearerFormat: 'JWT'
security:
  - BearerAuth:

Preview

openapi: '3.0.3'
info:
  title: 'My API'
  version: '1.0.0'
servers:
  - url: 'https://api.example.com'
paths:
  /api/resource:
    get:
      responses:
        200:
          description: 'Successful response'
          content:
            application/json:
              schema:
                type: 'object'
              example:
                id: 1
components:
  securitySchemes:
    BearerAuth:
      type: 'http'
      scheme: 'bearer'
      bearerFormat: 'JWT'
security:
  - BearerAuth:

All processing happens in your browser. No data is sent to any server.

About this tool

1
Set API info
Enter the API title, version, description, and base server URL.
2
Add paths and operations
Define endpoints with HTTP methods, parameters, request bodies, and response schemas.
3
Define schemas
Create reusable data models in the components section for request and response objects.
4
Export the spec
Download the complete OpenAPI 3.0 specification as YAML or JSON.

Define reusable schemas in #/components/schemas and reference them with $ref to avoid duplication.
Add example values to your schemas - they appear in generated documentation and mock servers.
Use tags to group related endpoints for cleaner documentation output.
Include all possible response codes (200, 400, 401, 404, 500) for complete API documentation.

Form-based OpenAPI 3.0 spec builder with no YAML/JSON editing required
Reusable schema components with $ref support
Path parameters, query parameters, headers, and request body configuration
Export as YAML or JSON with proper OpenAPI 3.0 structure
Live preview rendering with Swagger UI

Design a new REST API specification before writing any backend code
Generate OpenAPI docs for an existing API that lacks documentation
Create an API contract between frontend and backend teams
Produce a spec that can be imported into tools like Swagger, Postman, or code generators