JSON to TypeScript Converter

About this tool

Writing types by hand from a sample response is mechanical work that gets stale the moment the API changes. Generating them from an actual payload is faster and, more importantly, describes what the endpoint really returns rather than what the documentation claims.

The generator walks the JSON recursively. Every object becomes a named type, arrays are typed by unifying their elements, and structurally identical nested objects are emitted once and reused instead of producing near-duplicate interfaces.

How to use this tool

1. Paste a representative JSON response into the input panel.
2. Set the root type name — this is the name your top-level interface gets.
3. Choose interface, type alias or class, and set naming and optionality options.
4. Press Generate, then copy the code or download it as a .ts file.

Key features

• ✓interface, type alias or class output
• ✓Nested objects extracted into separate named types and reused when identical
• ✓Array element types unified, producing unions such as (string | number)[]
• ✓Optional properties for keys that are absent in some array elements
• ✓readonly modifiers and export keywords as options
• ✓Reserved words and invalid identifiers quoted so the output always compiles

Example

{"id":7,"owner":{"name":"Ada","email":"[email protected]"},"tags":["a"]}

export interface Owner {
  name: string;
  email: string;
}

export interface Root {
  id: number;
  owner: Owner;
  tags: string[];
}

Good to know

• Types are inferred from one sample. Fields that are null in the sample cannot be typed more precisely than null unless you enable nullable-widening.
• The generator cannot know that a string is a date, an enum or a branded id. Date detection is available as an option but is heuristic.
• Empty arrays yield unknown[], because there is no element to inspect.

Frequently asked questions