The tool walks the JSON tree recursively. Strings become string, numbers become number, booleans become boolean, arrays become Type[], and each nested object becomes its own named interface. The root object is named Root.
Names are derived from JSON keys using PascalCase. A key userAddress becomes UserAddress; the root is always Root. Nested objects get a name from their parent key.
Yes. Every nested object becomes a separate interface, and arrays are typed from their first element, so deeply nested API responses produce clean modular types.
A field whose sample value is null is typed as null. You should refine it by hand to optional (field?: T) or nullable (T | null) based on your real contract.
Yes. Copy the output into any .ts file. The interfaces are standard TypeScript and work immediately with the compiler and VS Code IntelliSense.
No. Generation runs entirely in your browser. Your JSON never leaves your device and is not logged or stored.
A 64-bit ID infers as number, but JavaScript loses precision past 2^53. Type such IDs as string to keep them exact.
Yes. An array like [1, "x"] becomes a union type (number | string)[] so the output stays accurate.
The output uses interfaces by default, which is idiomatic for object shapes. You can convert an interface to a type alias in your editor if you need unions or mapped types.
Yes. It is free, runs in your browser, requires no signup, and adds no watermark to your copied code.
Best practice is to scrub PII first. The tool is client-side, but pasted data can linger in clipboard history or screenshots — use placeholder values for anything private.
No. An empty {} has no fields to read, so give a non-empty example for a meaningful interface.
A JSON to TypeScript generator reads a sample JSON payload and writes TypeScript interface definitions that describe its shape. Instead of hand-typing every field of an API response, you paste the JSON and get copy-ready interfaces with correct types — strings become string, numbers become number, arrays become Type[], and nested objects become their own named interfaces. The whole thing runs in your browser. Start from clean input by running it through our JSON Formatter if the sample is unformatted.
field: null to field?: string or string | null where your contract allows it..ts file for autocomplete and compile-time checks.Working with encoded config values? Our Base64 Encoder/Decoder can reveal what is inside a blob before you type it.
string[]; mixed arrays become union types.Root.next.config.js or tailwind.config.js described as interfaces.Hand-writing interfaces for a deeply nested response is slow and error-prone — miss one field and TypeScript passes bad code through. A generator reads the real shape, so names and types match what the API actually returns. It is faster than typing it manually and safer than falling back to any. For runtime checks, pair the interfaces with a validator such as Zod.
null as a signal, not a type — mark the field optional or union it with null by hand.string to avoid JavaScript precision loss.All type inference happens locally in your browser with JavaScript. Your JSON sample is never sent to a server, which makes this safe for proprietary API responses and production configs. Still, scrub PII before pasting any real customer data into a web tool.
Developers reach for this generator the moment a new API response appears and they want types without writing them by hand. Paste the sample from Postman or DevTools, copy the interfaces, and your editor starts flagging typos immediately. It is far faster than typing each field and safer than falling back to any, which silently defeats TypeScript's checks.
When the payload mixes encoded blobs, our Base64 Encoder/Decoder reveals what is inside before you type it, and the JSON Formatter prettifies a minified response so the structure is easy to read. Everything runs locally, so you can iterate on several samples in a row with no account and no risk of leaking a sample to a third-party service.