How to use the JSON → TypeScript Interface
1. Paste any JSON object into the left panel.
2. Set the root interface name and toggle optional fields if needed.
3. Copy the generated TypeScript interfaces from the right panel.
What is it?
TypeScript interfaces define the shape of data structures, enabling type checking across your codebase. When working with AI APIs, JSON databases, or external services, manually writing interfaces for complex JSON responses is tedious and error-prone. This tool generates correct, nested TypeScript interfaces from any JSON sample in seconds.
Nested objects generate separate named interfaces. Arrays automatically use the element type followed by []. Null values type as null — in production code you may want to change these to T | null or T | undefined depending on your data guarantees.
Example
{"name":"Alice","age":30,"skills":["PHP","JS"],"address":{"city":"NYC"}}interface Address {
city: string;
}
interface Root {
name: string;
age: number;
skills: string[];
address: Address;
}Nested objects generate their own named interfaces. Arrays infer element type from the first item.
Benefits
Generate TypeScript interfaces from any API response in seconds
Paste a real JSON response and get accurate types with correct field names, types, and nesting — no manual type writing.
Eliminate hand-written types for complex third-party API responses
Manually writing interfaces for large API responses takes minutes and introduces naming mistakes — generate them correctly from sample data.
Detect optional vs required fields from the sample data
The tool infers optionality from null values and missing keys in the JSON sample — optional fields are typed correctly.
Bootstrap TypeScript types for a new API endpoint immediately
Start with generated interfaces and refine, rather than writing every field from scratch after reading the API documentation.
Frequently asked questions
How are null values typed?
Null values become the null type. In production TypeScript, you'll often want T | null or T | undefined. Toggle optional fields to add ? to all properties, which implies the value may be absent.
What if my array has mixed types?
The generator infers the type from the first element. If your array has mixed types (string | number), add a union type manually after generation. TypeScript supports this natively: (string | number)[].
Can I use type instead of interface?
The output uses interface, which is preferred for object shapes in TypeScript. You can manually change interface Root to type Root = { ... } — both work identically for plain objects.