JSON to TypeScript Interface Converter

What is JSON → TypeScript?

Converting JSON to TypeScript interfaces turns an untyped API response into a strongly-typed contract your editor can autocomplete and your compiler can check. Instead of hand-writing types for every endpoint, you paste a real response and get accurate interfaces — including nested objects, arrays, optional fields, and primitive inference (string, number, boolean).

How to convert JSON to TypeScript

1. 1Paste a representative JSON sample into the input pane (use a real API response for best results).
2. 2The right pane instantly renders TypeScript interfaces with inferred property types.
3. 3Rename the root interface to match your domain model (e.g. from Root to User).
4. 4Copy the output into a .ts file, or a types.d.ts declaration file.

Use Cases

Code Examples

{
  "id": 42,
  "name": "Ada",
  "roles": ["admin", "editor"],
  "profile": { "active": true }
}

interface Profile {
  active: boolean;
}

interface Root {
  id: number;
  name: string;
  roles: string[];
  profile: Profile;
}

Key Concepts

Structural typing

TypeScript checks compatibility by shape, not by name. Two interfaces with identical members are interchangeable — which is why generated interfaces work even if you rename them.

Optional properties

A field that is absent in some samples but present in others should be marked with `?`. A single sample can't detect this — merge multiple samples or edit the output.

type vs interface

`interface` is extendable and ideal for object shapes. `type` also handles unions and intersections. For plain JSON shapes, either works; interfaces are the common default.

Tips & Best Practices

• ▸One JSON sample can't reveal optional or nullable fields. Feed the tool a response that includes edge cases, or hand-tune `?` and `| null` afterward.
• ▸Rename the root `Root` interface immediately — descriptive names like `UserResponse` make the types far more useful.
• ▸For runtime validation (not just compile-time types), pair generated interfaces with a schema library like Zod or io-ts.
• ▸Arrays of objects are typed from the first element. If array items vary in shape, review the generated element type.