JSON to TypeScript Interface Generator
Paste any JSON object and instantly generate TypeScript interface declarations. Handles nested objects, arrays, and all primitive types — no server required.
What is JSON to TypeScript Interface Generator?
JSON to TypeScript conversion is the process of automatically generating TypeScript interface or type declarations from a JSON object structure. In modern TypeScript projects, API responses and data structures need to be typed to enable IDE autocompletion, catch type errors at compile time, and make code more maintainable and readable.
Writing TypeScript interfaces by hand for every API response can be tedious, especially for complex nested structures with dozens of fields. A JSON to TypeScript converter automates this work — paste a JSON sample, get the corresponding interface declarations in seconds, and immediately gain full type safety in your TypeScript code.
This tool analyzes your JSON structure recursively, infers the correct TypeScript type for each field (string, number, boolean, object, array), and generates clean, properly namespaced interface declarations with export keywords. Nested objects get their own interface definitions, and arrays are typed based on their element type.
How to Use
- 1
Paste your JSON
Paste your JSON object into the input field, or click 'Load Sample' to use a realistic user object example.
- 2
Set the root interface name
Enter the name for the root interface (default: Root). This name will be used for the top-level TypeScript interface.
- 3
Convert and copy
Click "Convert to TypeScript". The tool generates interface declarations for all nested objects. Copy the output and paste it into your TypeScript project.
Features
- Automatically infers TypeScript types from JSON values
- Handles nested objects by generating child interfaces
- Supports arrays — infers item type from first element
- Marks null values as optional (field?: type | null)
- Customizable root interface name
- Generates export keyword for module compatibility
- Works entirely in your browser — 100% private
- Free with no sign-up or limits
Frequently Asked Questions
- QWhat types does the converter support?
- The converter infers all basic TypeScript types: string, number, boolean, null, nested object interfaces, and typed arrays. For unknown or undefined values it falls back to 'unknown'.
- QHow are nested objects handled?
- Each nested object generates its own interface declaration. For example, a 'user.address' object creates an 'Address' interface, and the 'user' interface references it by name. All interfaces are output in the correct dependency order.
- QWhat happens with arrays?
- Arrays are typed based on the first element. If the first element is an object, a child interface is generated. If it's a primitive, the type is written as string[], number[], etc. Empty arrays become unknown[].
- QAre the generated interfaces accurate for production use?
- The generated interfaces are a good starting point but may need manual refinement. For example, if a field can be null in some responses, you should add '| null' to the type. The tool infers types from a single JSON sample, so union types and optional fields may need adjustment.
- QCan I use this for API response typing?
- Yes. The most common use case is pasting an API JSON response to generate TypeScript interfaces for your frontend or backend code. This saves significant time compared to writing interfaces by hand.
Try Other Tools
JSON Formatter
Format, validate and beautify JSON data instantly.
JWT Decoder
Decode and inspect JWT token headers and payloads client-side.
URL Encoder / Decoder
Encode and decode URLs and query string parameters.
Base64 Decode
Decode Base64 encoded strings back to plain text.