Generate TypeScript from JSON

Paste a JSON payload and get TypeScript interfaces describing it — with nested objects hoisted into named types rather than inlined — plus Go, Rust, Python and JSON Schema from the same inference.

Generate types from JSON

What the inference does

It walks a sample and describes what it finds: types for each field, optionality where a key is missing from some elements of an array, and unions where a field holds more than one type across samples. Nested objects become named interfaces rather than being inlined, which is the difference between output you can use and output you have to rewrite.

{
  "id": 1,
  "name": "Ada",
  "address": { "city": "London", "postcode": "W1J 9BW" },
  "tags": ["engineer", "mathematician"]
}

interface Address {
  city: string;
  postcode: string;
}

interface Root {
  id: number;
  name: string;
  address: Address;
  tags: string[];
}

Other targets

• TypeScript — interfaces, with nested types hoisted and named
• Go — structs with json: tags
• Rust — structs with serde derives
• Python — dataclasses with type hints
• JSON Schema — draft 2020-12, for validation rather than code

What inference cannot know

It describes the sample, not the contract. A field that happens to be present in your one example is marked required; a field that is null in the sample cannot be typed beyond null; and a date is a string, because in JSON it is. Treat the output as a first draft that saves you the typing, not as a specification.

Generate types from JSON