OpenAPI 3.0 to 3.1 Converter

How to use this developer tool

1. Paste a JSON-formatted API document or load the included sample.
2. Check that the document shape matches the label above the editor.
3. Select “Convert to OpenAPI 3.1” or press Ctrl/Cmd + Enter.
4. Review the summary and download the copy-ready result.

What this developer tool does

The converter handles mechanical keywords whose 3.1 representation can be derived without guessing API intent.

The original document is not modified in place; the output is a new formatted JSON document.

Example

The Sample button loads a small specification chosen for this operation. Running it produces the same structured fields shown in the output panel.

{
  "openapi": "3.0.3",
  "info": {
    "title": "Nullable API",
    "version": "1"
  },
  "components": {
    "schemas": {
      "User": {
        "type": "object",
        "nullable": true,
        "properties": {
          "nickname": {
            "type": "string",
            "nullable": true
          },
          "choice": {
            "oneOf": [
              {
                "type": "string"
              },
              {
                "type": "integer"
              }
            ]
          }
        }
      }
    }
  },
  "paths": {}
}

Use cases

• Review an API contract during a pull request.
• Prepare documentation or deterministic test fixtures.
• Find migration work before changing generators or clients.
• Export a focused report without sharing the source document.

Tips for reliable output

• Bundle remote references before running the page.
• Keep operation IDs stable across published versions.
• Prefer explicit examples for domain-specific values.
• Validate the complete document after applying generated output.
• Commit the original specification before a conversion.

Processing details

A deep copy is traversed once. The converter counts each keyword rewrite and leaves unknown extension fields untouched.

This is not a complete semantic migration. It does not rewrite every discriminator, example, reference-sibling, or webhook design decision; validate the output with a full OpenAPI 3.1 validator.