BYTETOOLS

JSON to TypeScript

Generate TypeScript interfaces from a JSON sample online. Infers types recursively, merges array shapes and marks optional keys — 100% in your browser.

  • Recursive type inference for nested objects and arrays
  • Merges object shapes across array elements
  • Marks keys optional when they vary between objects
  • Falls back to unknown[] for empty arrays
  • Configurable root interface name
  • 100% private — JSON never leaves your browser

How to use the JSON to TypeScript

  1. 1

    Paste a representative JSON sample into the input box.

  2. 2

    Set the root interface name (defaults to Root).

  3. 3

    Click Generate to infer TypeScript interfaces from the structure.

  4. 4

    Copy the interfaces to your clipboard or download them as a .ts file.

About the JSON to TypeScript

The ByteTools JSON to TypeScript generator converts a JSON sample into ready-to-use TypeScript interface definitions. It infers types recursively, creates nested interfaces for nested objects, merges the shapes of objects inside arrays and marks keys optional when they do not appear in every element.

It is perfect for developers typing an API response, building models from sample payloads, or replacing hand-written types that drift out of sync. Set the root interface name, paste your JSON, and copy strongly-typed interfaces you can drop straight into your codebase.

All inference runs 100% locally in your browser with JavaScript. Your JSON is never uploaded or stored, so you can safely generate types from private API responses, internal schemas and unreleased data structures.

Frequently asked questions

How do I generate TypeScript interfaces from JSON?

Paste a JSON sample, set a root interface name and click Generate. The tool walks the structure, creates an interface for each object, names nested interfaces from their keys and outputs valid TypeScript you can copy into your project.

How does it handle arrays of objects with different keys?

It merges every object in the array into a single interface. Keys present in all elements stay required, while keys that appear in only some elements are marked optional with a question mark, so the type covers every row safely.

What type does an empty array become?

An empty array is typed as unknown[] because there is no element to infer from. Once you provide a sample with data, the generator infers the element type and produces a precise array type instead.

Are nested objects turned into separate interfaces?

Yes. Each nested object becomes its own named interface, referenced from the parent. Identical structures are deduplicated so you do not get repeated interfaces for the same shape.

Is my JSON sent anywhere?

No. The entire conversion happens in your browser using JavaScript. Nothing is uploaded, logged or stored, so it is safe to generate types from confidential API payloads.

Related tools