JSON to TypeScript API

Turn any JSON payload into TypeScript interfaces online. Merges array item shapes, marks missing keys optional and dedupes identical structures. Free, no sign-up.

The JSON to TypeScript is also available as a free REST API. Send a POST request with a JSON body to https://dot.tools/api/tools/json-to-typescript — no authentication, no API key, CORS enabled. Successful calls return { "ok": true, "result": { … } }; failures return HTTP 400 or 422 with an error body.

Request body

Field	Type	Required	Description
`json`	string	required	The JSON document to generate TypeScript types for (max 5 MB).
`rootName`	string	required	Name for the root interface or type alias. Sanitized to PascalCase and must form a valid TypeScript identifier.
`exportKeyword`	boolean	required	Prefix every declaration with the export keyword.
`optionalWhenMissing`	boolean	required	Mark fields missing from some array items as optional (?). When false, they stay required with undefined added to the type union.

Response

Field	Type	Required	Description
`typescript`	string	required	The generated TypeScript declarations.
`interfaceCount`	number	required	Number of named interfaces emitted (excludes a root type alias).

Example request

curl -X POST https://dot.tools/api/tools/json-to-typescript \
  -H 'Content-Type: application/json' \
  -d '{
  "json": "{\n  \"name\": \"Ada Lovelace\",\n  \"active\": true,\n  \"level\": 9,\n  \"address\": {\n    \"city\": \"London\",\n    \"zip\": \"EC1\"\n  },\n  \"roles\": [\n    \"engineer\",\n    \"mathematician\"\n  ],\n  \"projects\": [\n    {\n      \"title\": \"Analytical Engine\",\n      \"year\": 1843\n    },\n    {\n      \"title\": \"Notes on the Engine\",\n      \"year\": 1843,\n      \"published\": true\n    }\n  ]\n}",
  "rootName": "Biography",
  "exportKeyword": true,
  "optionalWhenMissing": true
}'

Sample response

{
  "ok": true,
  "result": {
    "typescript": "export interface Biography {\n  name: string;\n  active: boolean;\n  level: number;\n  address: BiographyAddress;\n  roles: string[];\n  projects: BiographyProjectsItem[];\n}\n\nexport interface BiographyAddress {\n  city: string;\n  zip: string;\n}\n\nexport interface BiographyProjectsItem {\n  title: string;\n  year: number;\n  published?: boolean;\n}",
    "interfaceCount": 3
  }
}

Use the free JSON to TypeScript in your browser, read the JSON to TypeScript guide, or import the full OpenAPI specification.