Toolsvana→Developer Tools→JSON to TypeScript

JSON to TypeScript

Convert JSON objects to TypeScript interfaces and types

⚙️Options

Root Interface Name

Use interface (vs type alias)

Make all properties optional

Use readonly modifier

Export interfaces

💻Paste JSON

💻TypeScript Output

// TypeScript output will appear here...

Free Online JSON to TypeScript Converter

Our JSON to TypeScript converter transforms raw JSON data into properly typed TypeScript interfaces or type aliases in seconds. Paste any JSON object or array, click "Convert," and receive clean, production-ready TypeScript definitions that you can drop straight into your codebase. The tool handles nested objects, arrays with mixed types, null values, and deeply recursive structures automatically.

Customizable options give you full control over the output. Toggle between interface and type alias syntax, mark all properties as optional, apply the readonly modifier, add export keywords, and set a custom root interface name. Nested interfaces are automatically named based on parent keys and intelligently singularized, producing readable type names like "Project" from a "projects" array.

Whether you are consuming a REST API, migrating a JavaScript project to TypeScript, or documenting data shapes for your team, this JSON to TypeScript tool eliminates tedious manual type-writing. Everything runs in your browser -- your JSON data is never uploaded to any server, so it is safe to use with proprietary API responses and sensitive payloads.

Key Features

Recursive interface generation for deeply nested JSON objects
Smart array type detection with automatic union type support for mixed-type arrays
Toggle between interface and type alias syntax
Optional properties modifier for flexible type definitions
Readonly modifier to create immutable type contracts
Configurable export keyword for module-ready interfaces
Custom root interface naming
Intelligent nested interface naming with singularization (e.g., "projects" becomes "Project")
One-click copy of generated TypeScript code to clipboard
Preloaded sample JSON with nested objects, arrays, and null values for quick testing

How to Use the JSON to TypeScript Converter

Configure options: Set the root interface name and toggle preferences for interface vs. type, optional properties, readonly, and export keywords.
Paste your JSON: Enter or paste a JSON object or array into the left input panel. Click "Sample JSON" to load a demonstration payload.
Click Convert: Press "Convert to TypeScript" to generate the typed output in the right panel.
Review the output: Inspect the generated interfaces. Nested types appear above the root interface for clear dependency ordering.
Copy to your project: Click "Copy" to place the TypeScript code on your clipboard, then paste it into your .ts or .d.ts file.

Use Cases

Consuming REST APIs: Paste an API response to generate TypeScript interfaces that keep your frontend type-safe.
JavaScript to TypeScript migration: Convert JSON fixtures and mock data into typed definitions as part of a migration project.
Backend DTO creation: Generate Data Transfer Object types from sample request or response payloads for Node.js backends.
API documentation: Include generated interfaces in API docs so consumers know the exact shape of request and response data.
GraphQL type mapping: Use generated types as a starting point for GraphQL resolver type definitions.
Testing and mocking: Create typed mock data factories from real API responses for unit and integration tests.
Learning TypeScript: Students can see how JSON values map to TypeScript types, building intuition for the type system.

Frequently Asked Questions

Is this tool free?

Yes, the JSON to TypeScript converter is completely free with no registration or usage limits. Convert as many JSON payloads as you need.

Is my data secure?

Yes. All conversion happens locally in your browser. Your JSON data is never sent to any server, so you can safely convert proprietary API responses and internal data structures.

What is the difference between interface and type alias?

In TypeScript, both interface and type alias can describe object shapes. Interfaces support declaration merging and are generally preferred for public API contracts. Type aliases are more flexible and can represent unions, intersections, and primitive types. Choose whichever aligns with your project's conventions.

Does it handle arrays with mixed types?

Yes. If an array contains elements of different types (e.g., strings and objects), the converter generates a union type like (string | MyObject)[]. Object shapes from all elements are merged into a single comprehensive interface.

Can I convert JSON arrays at the root level?

Yes. If your root JSON is an array of objects, the converter creates an interface for the array item and a type alias for the root array. If the array contains only primitives, it generates a simple type alias like "type RootObject = string[]."

Tips & Best Practices

Use a representative JSON sample: Include all possible fields in your sample so the generated interface captures the full data shape.
Set a meaningful root name: Change "RootObject" to something descriptive like "UserResponse" or "ProductData" for better code readability.
Enable optional for partial data: If your API returns different fields depending on context, mark properties as optional to avoid compilation errors.
Use readonly for immutable state: When the generated types represent state that should not be mutated (e.g., Redux store slices), enable the readonly modifier.
Review nested naming: Check that auto-generated nested interface names make sense. Rename them in your code if the singularization produces awkward results.
Combine with JSON Schema: For complete validation, generate a JSON Schema alongside TypeScript types to validate data at runtime as well as compile time.