{ } JSON Workbench0 network requests. Check DevTools

"JSON to TypeScript":{ }

Paste a JSON sample and get clean TypeScript interfaces. Nested objects become named types, arrays become typed collections, and nullable fields are handled. Powered by quicktype's inference engine running 100% in your browser: zero network requests, so real API payloads stay on your machine.

What is a JSON to TypeScript converter?

Hand-writing interfaces for an API response is slow and error-prone. This tool infers TypeScript interfaces from a JSON sample: nested objects become named types, arrays become typed collections, and null/missing values become optional fields. It runs quicktype's inference engine entirely in your browser, so real API payloads (often containing user data or credentials) never leave your machine.

TypeScript mapping notes

  • Optional fields: a key missing from some objects in a sample array becomes key?: type.
  • Mixed-type values become union types (string | number).
  • Integers and floats are both number, since TypeScript has one numeric type.

How to use

  1. Paste a JSON sample (an API response works well) into the Input pane.
  2. Generated TypeScript interfaces appear instantly. Nested objects become their own named types.
  3. Non-standard JSON (single quotes, trailing commas, comments) is auto-repaired first.
  4. Copy the code into your project.

Examples

JSON → TypeScript interfaces

Input
{
  "id": 42,
  "name": "workbench",
  "owner": { "email": "[email protected]", "active": true }
}
Output
interface Root {
  id:    number;
  name:  string;
  owner: Owner;
}

interface Owner {
  email:  string;
  active: boolean;
}

FAQ

How do I convert JSON to TypeScript types?

Paste any JSON sample. The interfaces are inferred from the values and nesting, entirely in your browser. Nothing is uploaded.

How are nested objects handled?

Each distinct nested object becomes its own named type, referenced from the parent, arrays of objects included.

What about optional or null fields?

Fields that are null or missing in parts of the sample are typed as optional/nullable in the generated code.

Can I paste multiple samples?

Paste an array of objects: the type is inferred from the union of all items, which catches optional fields a single sample would miss.

Interface or type alias?

Interfaces are generated because they merge and extend cleanly. Converting to type aliases is a find-and-replace if your style guide prefers them.

Is my JSON uploaded?

No. Generation runs 100% in your browser via quicktype's engine. Check DevTools: zero network requests.

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