JSON Schema to OpenAPI Converter — Free Online

Convert JSON Schema (Draft-07 / 2020-12) to a minimal OpenAPI document — choose openapi 3.0.3 or 3.1.0 (version field; Schema Objects stay OAS 3.0-oriented). 100% in-browser, nothing uploaded.

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JSON Schema to OpenAPI documentation

Convert JSON Schema to a minimal OpenAPI document (openapi 3.0.3 or 3.1.0 version field).

Developer notes

• Converts Draft-07 / 2020-12 JSON Schema to OpenAPI Schema Objects via @openapi-contrib/json-schema-to-openapi-schema. • Output is a minimal OpenAPI document (info, empty paths, components.schemas) with openapi 3.0.3 (default) or 3.1.0. • $defs / definitions become named schemas; a root-only schema becomes Root (or title). • External / http(s) $ref are rejected — never fetched. • JSON input only (YAML rejected). • Max input 512 KiB.

Options

OpenAPI version

Sets the document openapi field to 3.0.3 (default) or 3.1.0. Schema objects still come from the OAS 3.0-oriented converter (e.g. nullable); choose 3.1.0 when your toolchain expects that version string.

Use cases

• Turn a JSON Schema model into an OpenAPI components.schemas starter. • Chain into Validate OpenAPI after conversion. • Share a single-file OpenAPI stub from an existing schema.

Examples

JSON Schema $defs → OpenAPI components.schemas

Before

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$defs": {
    "Pet": {
      "type": "object",
      "required": [
        "id",
        "name"
      ],
      "properties": {
        "id": {
          "type": "integer"
        },
        "name": {
          "type": "string"
        }
      }
    }
  }
}

After

{
  "openapi": "3.0.3",
  "info": { "title": "Converted from JSON Schema", "version": "1.0.0" },
  "paths": {},
  "components": { "schemas": { "Pet": { ... } } }
}

External $ref rejected

Before

{
  "$ref": "https://example.com/schemas/pet.json"
}

After

Error: external $ref not supported

JSON Schema to OpenAPI FAQ

Common questions

Which OpenAPI version is produced?

Choose <strong>3.0.3</strong> (default) or <strong>3.1.0</strong> in the toolbar. This sets the document <code>openapi</code> field. Schema Objects still come from the OAS 3.0-oriented converter (e.g. <code>nullable</code>) — not a full OAS 3.1 Schema Object rewrite. See Options.