JSON to TypeScript Converter - Generate Interfaces Locally

Free online JSON to TypeScript converter. Instantly generate TypeScript interfaces and types from your JSON payloads. 100% private, client-side code generation.

Click for theater mode

All inference runs locally in your browser. JSON is not uploaded.

Generated TypeScript interfaces and types will appear here.

How to Use

  1. Paste a JSON object or API response into the input editor, or click "Load API Sample" to start with an order response example.
  2. Set the "Root Type Name" to match your model, such as OrderResponse, UserProfile, or SearchResult.
  3. Choose interface or type output, then decide whether nested objects should become named declarations or inline object types.
  4. The tool parses JSON locally and generates highlighted TypeScript code on the right.
  5. Click "Copy TypeScript" or "Download .ts" and paste the generated code into your frontend, Node.js, or shared type files.

Core Features

  • JSON to TypeScript Converter: Paste a JSON object or API response and instantly generate TypeScript code for your .ts or .tsx files.
  • Generate TypeScript Interfaces: Customize the root type name, choose interface or type, and output nested objects as named declarations or inline structures.
  • Nested Object and Array Inference: Recursively detects string, number, boolean, null, arrays, and objects. Mixed object arrays are merged with optional properties.
  • Copy to Clipboard: Copy generated TypeScript in one click or download a .ts file to avoid typo-prone manual interface writing.
  • 100% Client-Side and Private: JSON parsing and TypeScript generation run locally in your browser. API payloads and internal schemas are not uploaded.

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Calculation Logic

The tool first validates input with the browser's native JSON.parse(), then recursively walks the parsed value to infer TypeScript types: strings become string, numbers become number, booleans become boolean, null remains null, and arrays are converted into array or union types based on their contents.

When an array contains multiple objects, the tool merges their keys; fields that appear in only some items become optional properties with ?. Nested objects can be emitted as separate named interfaces or as inline object structures. The entire inference process runs in the current browser JavaScript runtime and does not call AI models, backend services, or external APIs.

FAQ

Why convert JSON to TypeScript?

TypeScript interfaces give API responses, config objects, and frontend state autocomplete, compile-time checks, and clearer data contracts, reducing mistakes from manually maintained fields.

Does this support nested JSON objects?

Yes. The converter recursively infers nested objects and arrays of objects, and can output either separate named interfaces or inline object shapes.

What happens when array items have different fields?

For arrays of objects, the tool merges keys and marks missing fields as optional. Mixed primitive arrays become union types, such as (string | number)[].

Is it safe to paste confidential API JSON?

Yes. JSON parsing and type inference run locally in your browser. EasyTools does not upload, store, or transmit your JSON content.

Can this generate Go, Rust, or C# types?

No. This tool focuses on JSON to TypeScript and only generates TypeScript interfaces or types.