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JSON → TypeScript Interface

Paste any JSON and instantly get a fully typed TypeScript interface. Handles nested objects, arrays, and optional fields.

Options:

JSON Input

TypeScript Interface


    
⚙️ How the JSON → TypeScript Converter Works

The converter uses a depth-first traversal algorithm to walk the JSON tree, inferring types for every value and creating nested interfaces where needed.

string → string number → number boolean → boolean null → null / ? (optional) array → Type[] (or Union[] if mixed) object → Interface (recursive)
1
Parsing: The JSON is validated using the browser's native JSON.parse(). If it fails, an error is caught and displayed.
2
Type Inference: The typeof operator evaluates primitive values. Arrays map through their elements to build a unique set of types (e.g., (string | number)[]).
3
Recursive Objects: When an object is encountered, a new named interface is spun up. The parent interface references this new child interface by name (e.g., address: Address;).
Why Top-Down matters: The algorithm collects all nested interfaces in a Map, guaranteeing that dependencies are declared correctly before the root interface.

All logic runs entirely client-side. No data is sent to a server.

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