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JSON to TypeScript

Auto-generate TypeScript interfaces from any JSON — nested objects · optional fields · readonly · export · 100% Free

JSON INPUT

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⚙ OPTIONS

Interface Name

Keyword

Array format

exportPrepend export keywordreadonlyMark all properties readonlyoptional fieldsMark missing keys as ?null → nullnull stays null (not unknown)semicolonsEnd each property with ;

TYPESCRIPT OUTPUT

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TypeScript interfaces appear here

Paste JSON on the left · click a Sample · or drag & drop a .json file

export interface User {
  id: number;
  name: string;
  active: boolean;
  address: Address;
}

Ctrl+Enter GenerateCtrl+Shift+C Copy outputCtrl+L ClearCtrl+S Download .tsP Pin

What is JSON to TypeScript Interface Generation?

This tool analyses the structure of your JSON data and automatically generates TypeScript interface or type declarations — saving you the time of writing them manually. It infers string, number, boolean, null, nested object interfaces, and typed arrays. When your JSON is an array of objects, optional fields are detected automatically.

How Nested Objects Are Handled

Every nested JSON object generates its own named TypeScript interface. For example, if your JSON has "address": { "city": "Ahmedabad" }, the tool generates a separate Address interface and references it as address: Address in the parent interface — matching real-world TypeScript project structure.

Frequently Asked Questions

What is JSON to TypeScript interface generation?

This tool analyses the structure of your JSON data and automatically generates TypeScript interface or type declarations — saving you the time of writing them manually. It detects strings, numbers, booleans, arrays, nested objects, and optional fields.

How are optional fields detected?

When your JSON is an array of objects, the tool compares all items. Keys that don't appear in every object are marked as optional (?) because they may be absent in runtime data.

What is the difference between interface and type?

In TypeScript, interface and type alias are mostly interchangeable for object shapes. Interfaces support declaration merging and are preferred for public API shapes. Type aliases are more flexible and support union/intersection types directly.

Can it handle nested JSON?

Yes. Every nested object generates its own named interface, referenced by the parent. For example, a nested "address" object becomes an Address interface, and the parent has address: Address.

What does "readonly" do?

Adding the readonly modifier to each property means TypeScript will prevent you from reassigning those fields at compile time — useful for immutable data models.