JSON to TypeScript Generator — Convert JSON to TS Interfaces
Auto-generate TypeScript interfaces from any JSON — nested objects · optional fields · readonly · export · 100% Free
export interface User {
id: number;
name: string;
active: boolean;
address: Address;
}Writing TypeScript interfaces by hand from API JSON responses is tedious and error-prone, especially for large nested structures. This generator reads your JSON and produces proper TypeScript interfaces with correct types, optional fields and nested interface definitions — in under a second. Works with any JSON: API responses, config files, database schemas or mock data.
What is JSON to TypeScript Interface Generation?
This tool analyses the structure of your JSON data and automatically generates TypeScript interface or type declarations — saving you the time of writing them manually. It infers string, number, boolean, null, nested object interfaces, and typed arrays. When your JSON is an array of objects, optional fields are detected automatically.
How Nested Objects Are Handled
Every nested JSON object generates its own named TypeScript interface. For example, if your JSON has "address": { "city": "Ahmedabad" }, the tool generates a separate Address interface and references it as address: Address in the parent interface — matching real-world TypeScript project structure.
Frequently Asked Questions
Why should I generate TypeScript types from JSON instead of writing them manually?
Manual typing is slow and inconsistent. A 50-field API response takes 15–30 minutes to type manually. Generators do it in 1 second with zero typos. Auto-generated types: match the actual API structure, handle nested types correctly, generate consistent naming. Then review and refine — don't write from scratch.
How does the TypeScript generator handle null values in JSON?
null in JSON generates type: string | null (or number | null etc.). If a field is sometimes null and sometimes a value, use optional with null: field?: string | null. The generator detects null values and includes | null in the type. You should also mark such fields as optional (?) if they can be absent entirely.
What is the difference between TypeScript interface and type alias for JSON types?
Interfaces: can be extended (interface B extends A), merged across files (declaration merging), better for OOP patterns. Type aliases: support union types (type A = B | C), mapped types, conditional types, better for functional patterns. For JSON API types, both work equally well. Use interface for extensible models, type for unions and utilities.
How do I handle JSON arrays in TypeScript types?
Array of strings: string[]. Array of numbers: number[]. Array of objects: User[] (after defining User interface). Mixed array: (string | number)[]. Array of arrays: string[][]. The generator automatically detects array types from your JSON and generates correct TypeScript array notation.