Generate TypeScript from JSON — Auto TypeScript Code Generator
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;
}Automatically generating TypeScript code from JSON is a superpower for frontend and full-stack developers. Instead of manually typing out interfaces for every API endpoint, paste the JSON response here and get complete, production-ready TypeScript definitions in seconds. The generator handles all edge cases: mixed-type arrays, deeply nested structures, null values and empty objects.
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
What TypeScript code does the generator produce?
The generator produces: (1) Separate interface for each nested object. (2) Proper type for each field (string, number, boolean, null, Array<T>). (3) Optional modifier (?) for fields that could be absent. (4) Nested interface references (user: UserInterface). (5) Export statements for use across files. Output is ready to paste into your .ts or .d.ts files.
How do I handle JSON with inconsistent field types?
If a field is sometimes a string and sometimes a number across different API calls, generate a union type: field: string | number. The generator sees a single sample — if your JSON shows "price": "99.99" (string), it generates string. If you know it can also be a number, manually add: price: string | number. Use multiple samples for better type inference.
Can I generate TypeScript from multiple JSON samples for better accuracy?
Yes — for more accurate types, sample multiple API responses and merge. Tools like json-to-ts npm package and quicktype.io accept multiple samples and infer the most accurate types (detecting optional fields that don't appear in all samples, detecting union types from varied values). For one-off generation, single sample is usually sufficient.
How do I integrate TypeScript generation into my development workflow?
Options: (1) quicktype CLI: quicktype -s json input.json -o types.ts (CI-friendly). (2) openapi-typescript: generates types from OpenAPI spec (best for documented APIs). (3) graphql-code-generator: for GraphQL APIs. (4) json-schema-to-typescript: from JSON Schema. Use CLI tools in build pipeline — browser tools are for quick one-off generation.