Paste JSON to instantly generate TypeScript interfaces with proper types.
Input JSON:
Output TypeScript:
Have questions? Check our FAQ page.
TypeScript interfaces provide compile-time type safety for your JavaScript code. When working with APIs that return JSON data, defining proper TypeScript interfaces ensures your code correctly handles the data structure - catching errors before they reach production.
Manually writing interfaces for complex API responses is tedious and error-prone. This tool automates the process by analyzing your JSON data and generating accurate TypeScript interfaces with proper types for strings, numbers, booleans, arrays, and nested objects.
string[], number[])any (since the type can't be inferred)For best results, use a complete JSON sample that includes all possible fields. The generated interfaces serve as a starting point - you may want to add optional markers (?), union types, or rename interfaces to match your project conventions.
Complex API responses often contain nested objects and arrays. Here's how the tool handles them:
Input JSON:
Output TypeScript:
anyWhen a field is null, the tool can't determine its actual type. Solution: Use a sample JSON where all fields have values, or manually replace any with the correct type like string | null.
any[]An empty array [] provides no type information. Solution: Use a sample with at least one array element, or manually specify the array type (e.g., string[] or User[]).
?The tool generates required fields by default since it can't know which fields are optional from a single sample. Solution: Manually add ? to optional fields: middleName?: string;
If a field can be multiple types (e.g., string | number), the tool uses the type from your sample. Solution: Manually add union types where needed, or use multiple samples to identify variations.
This tool generates interface declarations, which are the standard way to define object shapes in TypeScript. Interfaces can be extended and merged, making them ideal for API response types. If you prefer type aliases, you can easily convert: type User = { ... }.
The tool generates generic names like Root, Item, and property-based names. After generating, rename interfaces to match your domain (e.g., Root ? ApiResponse, Item ? Product).
Standard JSON doesn't allow comments. If your JSON has comments (common in config files), they'll cause parsing errors. Remove comments first, or use our Fix JSON tool which can handle some non-standard formats.
For objects with dynamic keys (like {"user_123": {...}}), manually use TypeScript index signatures: interface Users { [key: string]: User; }. The tool generates literal property names from your sample.
No. All processing happens locally in your browser. Your JSON never leaves your machine, making this tool safe for sensitive API responses, credentials, and proprietary data.
This tool runs 100% in your browser. Your JSON data is never sent to any server - it's processed locally using JavaScript. This makes it safe for sensitive data like API responses with authentication tokens, private configuration files, and proprietary business data. No data is stored, logged, or transmitted.