JSON to TypeScript

1. Paste your JSON in the input area on the left.
2. Optionally change the root interface name (default is "Root").
3. Choose between "interface" and "type" alias output.
4. Toggle optional properties or export keywords as needed.
5. The generated TypeScript appears instantly on the right.
6. Click "Copy" to copy the result to your clipboard.

What is JSON to TypeScript Conversion?

JSON to TypeScript conversion takes a JSON object and generates TypeScript interface or type alias definitions that describe its shape. TypeScript is a superset of JavaScript that adds static type checking, and interfaces define the expected structure of objects at compile time. By generating these definitions from real JSON data (such as an API response), you get accurate type definitions without manually writing them. This eliminates a common source of bugs where the code assumes a different structure than what the API actually returns.

How the Conversion Works

The tool parses your JSON input and recursively walks through the data structure. For each object, it creates an interface with properties matching the JSON keys and their inferred types. Nested objects are extracted into separate named interfaces to keep the output clean and reusable. Arrays are typed based on the first element as a representative sample. Primitive values are mapped to their TypeScript equivalents: strings become string, numbers become number, booleans become boolean, and null becomes null. You can choose between interface (supports declaration merging and extends) and type alias (supports unions and intersections) output formats. All conversion happens entirely in your browser.

Common Use Cases

• Typing REST API responses from backend services or third-party APIs
• Creating type definitions for JSON configuration files
• Bootstrapping TypeScript interfaces for database models
• Generating types from sample data during rapid prototyping
• Documenting data structures for team collaboration
• Converting GraphQL or OpenAPI response samples to TypeScript types

Interface vs Type Alias in TypeScript

Both interface and type can describe object shapes in TypeScript, but they have different strengths. Interfaces support declaration merging, meaning you can define the same interface in multiple places and TypeScript will combine them. Interfaces can also be extended with extends for inheritance. Type aliases are more flexible and can represent unions (string | number), intersections, mapped types, and conditional types. For plain object shapes like API responses, interfaces are the conventional choice and provide slightly better error messages. Use type aliases when you need advanced type features or when defining unions and utility types.

For validating your JSON before conversion, use the JSON Validator. For formatting JSON data, try the JSON Formatter. For schema-based validation, see the JSON Schema Validator.