How are arrays typed?

The element type is inferred from the array’s items — ["a","b"] becomes string[]. Mixed arrays widen to a union like (string | number)[]; empty arrays fall back to unknown[] or any[].

Answer

How to convert JSON to a TypeScript interface

Generate TypeScript interfaces or types from a JSON sample instantly in your browser.

A JSON-to-TypeScript converter infers a type from a JSON sample: each key becomes a property and each value’s shape becomes its type (string, number, boolean, arrays, and nested interfaces). Paste your JSON and it generates ready-to-use interfaces.

Input

{ "id": 1, "name": "Ann", "active": true }

Output

interface Root {
  id: number;
  name: string;
  active: boolean;
}

Nested objects become their own interfaces; arrays infer an element type like string[].

Open the JSON to TypeScript → Free · runs in your browser · nothing uploaded

Steps

Open the JSON → TypeScript tool and paste a representative JSON sample.
Read the generated interface(s) and copy them into your codebase.
Provide a sample that includes every field (and realistic values) so types are inferred accurately.
Rename the root interface to match your domain after pasting.

Frequently asked questions

How are arrays typed?: The element type is inferred from the array’s items — ["a","b"] becomes string[]. Mixed arrays widen to a union like (string | number)[]; empty arrays fall back to unknown[] or any[].

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