Free JSON to TypeScript Tool

The JSON to TypeScript converter is a free online tool that automatically generates TypeScript interfaces from JSON objects, saving you time writing type definitions.

Yes, it is completely free with no registration required. All conversion happens client-side in your browser.

Yes, the JSON to TypeScript converter handles deeply nested objects and arrays, generating proper TypeScript interfaces for each level.

Absolutely. The JSON to TypeScript Tool processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the JSON to TypeScript Tool is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the JSON to TypeScript Tool in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The JSON to TypeScript Tool works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

An interface and a type alias can describe the same JSON shape, but they behave differently. Interfaces are open: you can declare the same interface twice and TypeScript merges the members, and they read cleanly for object models like an API response. Type aliases cannot be reopened, but they are more flexible for unions, intersections, and mapped types, so they suit fields that can be one of several shapes. For most plain API payloads either works and the choice is stylistic, though many teams default to interfaces for object models and reach for type aliases when a union is involved. This converter generates both from the same JSON, plus Zod schemas and JSON Schema, so you can switch the output format with one click and compare them. It also extracts nested objects into their own named declarations either way. Paste your JSON, pick interface or type alias, and copy the result straight into a .ts file.

A single response only shows the fields that happened to be present that one time. If an endpoint sometimes omits avatar_url or returns null for a nickname, a converter that sees just one payload will mark those fields as always required, and your types will lie about the real data. The fix is to merge several samples so the tool can compare them. This converter accepts multiple JSON examples and merges their shapes: a key that appears in every sample stays required, while a key missing from any sample is inferred as optional. The result reflects how the API actually behaves across responses rather than one lucky payload, which means fewer runtime surprises when a field you assumed was always there turns out to be missing. Paste a few different responses, let the tool reconcile them, and you get accurate required-versus-optional fields automatically.

A plain interface only exists at compile time, so it cannot check that data arriving at runtime actually matches. Zod solves that by giving you a schema you can call .parse() on to validate incoming JSON and infer a matching type from the same definition. In this converter, switch the output format from interface to Zod schema and it generates a z.object({ ... }) declaration from your JSON, with nested objects expressed as their own schemas. Optional and nullable handling carry over, so a field that is sometimes missing becomes .optional() and a field that can be null becomes .nullable(). There is also a one-click Zod Validation preset that sets sensible defaults. Paste your JSON, choose the Zod output, and copy a schema that both types and validates your data.

By default every JSON string maps to the broad TypeScript type string, which is correct but loses meaning. When you enable special-type detection, the converter inspects string values and recognizes common formats — UUIDs, email addresses, URLs, and ISO date strings — so you get more descriptive output instead of a generic string everywhere. It also handles arrays more intelligently: fixed-length mixed-type arrays are detected as tuples rather than being widened to a single element type, which keeps positional data accurate. These behaviors are off by default so you stay in control of how aggressive the inference is, and presets like Strict and API Response turn the relevant ones on for you in a single click. Toggle special-type detection above the input, paste your JSON, and the generated types will reflect the actual shape and meaning of your values rather than collapsing everything to string.

JSON uses null for absent values, but TypeScript gives you three ways to model that, and the right one depends on your code. Using undefined pairs naturally with optional properties and is what you get when a key is simply missing from an object. Using literal null matches the JSON wire format exactly, which is useful when you serialize back to an API. A T | null union keeps the field required while allowing an explicit null, forcing callers to handle the empty case. This converter exposes a null-handling option so you can pick null, undefined, or the nullable union, and the choice applies consistently across every generated field. Set your preference above the input, paste your JSON, and copy types that match how your application treats missing data.