JSON to TypeScript

Convert JSON payloads into strongly typed TypeScript interface declarations recursively.

Root Name:

Declaration Type:

Make Properties Optional (?)

JSON Payload Input

TypeScript Type Declarations

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Learn About This Tool

Accelerating Frontend Development with TypeScript Generators

TypeScript enforces type safety by declaring interfaces for API parameters. Writing interface declarations manually for complex API responses is tedious and error-prone. This tool generates clean TypeScript code in real time from raw JSON payloads:

// Sample JSON payload:
{
  "id": 1,
  "isActive": true
}

// Generated TypeScript Interface:
interface RootObject {
  id: number;
  isActive: boolean;
}

Automatically map property names to matching types (string, number, boolean)
Recursively build nested sub-interfaces for child objects
Avoid type mismatch exceptions during API integrations
Support arrays, nulls, and mixed types dynamically

Customizable Output Declarations: Interface, Type, or Class

Developers use different architectural patterns to declare models. You can choose to export properties as standard interface structures, type aliases, or class definitions. For general validation frameworks instead of direct type declarations, check out our JSON Schema Tool to compile schemas recursively.

Interface format is recommended for public APIs and extensible frameworks
Type format is ideal for static objects and unions
Class format helps initialize objects with parameters
Optional toggle (?) flags all keys as non-mandatory for safety

Validating JSON Syntax in Real Time

Our browser-native compiler parses the input data string using a local JSON parse validation check. If a syntax error is found, use our JSON Formatter to auto-fix and format your data layout instantly before conversion.

Catches JSON format violations before generating types
Performs all formatting checks client-side for maximum confidentiality
No data is shared over HTTP requests to external APIs
Instantly converts payload arrays or simple nested layouts

How to Use JSON to TypeScript

Paste JSON Input

Enter your raw JSON object or array structure in the left input panel.

Configure TypeScript Options

Define a custom Root Interface Name, choose output style (interface/type/class), and set optional flags.

Copy Generated Code

The compiler will render typed models instantly in the right panel. Click Copy Types to copy.

Common questions

What does this tool do?

It parses a JSON object or array, infers the data types of its fields, and automatically generates valid TypeScript declarations (interfaces, types, or classes).

How does it handle nested JSON objects?

It recursively parses child objects and automatically extracts them into separate, unique interfaces linked by their parent keys.

What happens to array types?

The tool checks the items in the array. If all items share a single type, it generates a standard array type (e.g. string[]). If items have mixed types, it creates a union type array.

Can I make all interface properties optional?

Yes. Toggle the 'Make Properties Optional' option to append a question mark (?) after all generated keys.

Why does it show a JSON syntax error?

The input must be a valid JSON string. Ensure keys are double-quoted, commas are placed correctly, and there are no trailing commas.

Is my API payload data secure?

Yes. All JSON parsing and TypeScript string compilations occur entirely in your browser. No data is sent to external servers.

How are null or empty array values typed?

If a property value is null, the tool infers it as `any` or `null`. For empty arrays `[]`, it defaults to `any[]` since there is no item data to determine the specific element type.

How does the tool choose interface names for nested objects?

It sanitizes the object key (e.g. converting `user_profile` to PascalCase `UserProfile`) and verifies it doesn't collide with existing interface names, appending a numeric suffix if needed to maintain uniqueness.

Can it convert a JSON array as the root input?

Yes. If the root input is a JSON array, the tool parses the first item's schema to build the type interface and labels the root output type as an array of that interface (e.g., `type RootObject = RootInterface[]`).

Does it support custom classes with constructor methods?

The class export option generates ES6 class structures with declared fields. It compiles clean type-safe structures that you can copy and decorate with your custom constructor or helper methods.