Swagger 2 to OpenAPI 3 Converter

{
  "swagger": "2.0",
  "info": {
    "title": "Orders API",
    "version": "1.0.0"
  },
  "host": "api.example.com",
  "schemes": [
    "https"
  ],
  "consumes": [
    "application/json"
  ],
  "paths": {
    "/orders": {
      "post": {
        "parameters": [
          {
            "name": "order",
            "in": "body",
            "required": true,
            "schema": {
              "$ref": "#/definitions/Order"
            }
          }
        ],
        "responses": {
          "201": {
            "description": "Created"
          }
        }
      }
    }
  },
  "definitions": {
    "Order": {
      "type": "object",
      "properties": {
        "id": {
          "type": "string"
        }
      }
    }
  }
}

{
  "openapi": "3.0.3",
  "info": {
    "title": "Orders API",
    "version": "1.0.0"
  },
  "servers": [
    {
      "url": "https://api.example.com"
    }
  ],
  "paths": {
    "/orders": {
      "post": {
        "responses": {
          "201": {
            "description": "Created"
          }
        },
        "requestBody": {
          "required": true,
          "content": {
            "application/json": {
              "schema": {
                "$ref": "#/components/schemas/Order"
              }
            }
          },
          "x-original-name": "order"
        }
      }
    }
  },
  "components": {
    "schemas": {
      "Order": {
        "type": "object",
        "properties": {
          "id": {
            "type": "string"
          }
        }
      }
    }
  }
}

The body parameter becomes requestBody — its name has no 3.0 field, so it survives as x-original-name — and the definition moves to components/schemas with its $ref rewritten.

swagger: "2.0"
info:
  title: Status API
  version: "1.0"
host: status.example.com
basePath: /api
schemes:
  - https
  - http
paths:
  /health:
    get:
      responses:
        "200":
          description: Healthy

openapi: 3.0.3
info:
  title: Status API
  version: "1.0"
servers:
  - url: https://status.example.com/api
  - url: http://status.example.com/api
paths:
  /health:
    get:
      responses:
        "200":
          description: Healthy

host, basePath and both schemes combine into two servers, in scheme order — the cartesian rule. YAML in, YAML out.

swagger: "2.0"
info:
  title: Import API
  version: "2.0"
paths:
  /import:
    post:
      consumes:
        - multipart/form-data
      parameters:
        - name: file
          in: formData
          type: file
          required: true
        - name: mode
          in: formData
          type: string
          enum:
            - merge
            - replace
      responses:
        "202":
          description: Accepted

{
  "openapi": "3.0.3",
  "info": {
    "title": "Import API",
    "version": "2.0"
  },
  "paths": {
    "/import": {
      "post": {
        "responses": {
          "202": {
            "description": "Accepted"
          }
        },
        "requestBody": {
          "content": {
            "multipart/form-data": {
              "schema": {
                "type": "object",
                "properties": {
                  "file": {
                    "type": "string",
                    "format": "binary"
                  },
                  "mode": {
                    "type": "string",
                    "enum": [
                      "merge",
                      "replace"
                    ]
                  }
                },
                "required": [
                  "file"
                ]
              }
            }
          },
          "required": true
        }
      }
    }
  }
}

Both formData parameters merge into one multipart/form-data schema and the file field becomes type: string, format: binary. The input was YAML — the output format is a setting, not an accident.