JSON to TypeScript

Generate TypeScript interfaces automatically from any JSON object

What is it and how does it work?

A JSON to TypeScript converter reads a JSON object and generates the TypeScript interfaces or type aliases that describe its shape. Instead of hand-writing a type for every API response — naming each field, guessing whether a value is a string or number, and nesting interfaces for nested objects — you paste a real example and get accurate types instantly. It infers each property's type from the value, creates named interfaces for nested objects, and types arrays by their elements, so your editor immediately knows the structure.

This is one of the highest-value shortcuts in TypeScript work because it removes the tedious, error-prone step of mirroring an API by hand and keeps your types honest to the real data. The result gives you autocomplete and compile-time checking the moment you import it, catching typos and shape mismatches before they reach runtime. This tool generates the types entirely in your browser, so even private API responses never leave your machine.

Common use cases

• Typing an API response: paste a sample response and get ready-to-use interfaces for the data your app receives.
• Modelling config or data files: turn a JSON config into a typed interface so your editor validates it as you work.
• Speeding up prototyping: generate types from mock data instantly instead of writing them by hand for every endpoint.

Frequently asked questions

Should I use interfaces or type aliases?

For object shapes both work; interfaces are conventional for data models and support declaration merging and extension, while type aliases are handy for unions and more complex compositions. The generated interfaces are a solid default you can rename or refactor freely.

How are nested objects handled?

Each nested object becomes its own named interface, referenced from the parent. This keeps the output readable and reusable rather than producing one deeply inlined type, mirroring how you would structure types by hand.

How accurate are the inferred types?

Types are inferred from the example you provide, so they are exact for that sample but only as complete as the data shown. If a field can be null, optional or vary in type across responses, review and widen the generated type to cover every case the API can return.

What happens with empty arrays or null values?

An empty array gives no element to infer from, and a null value carries no concrete type, so these often resolve to a broad type like any[] or null. Provide a fuller example, or refine those fields manually, to capture the intended type.

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