JSON to TypeScript

Infer TypeScript type definitions from JSON

Runs in your browserUtility02 — Converters

What is JSON to TypeScript?

A JSON to TypeScript converter reads a sample JSON payload and infers the matching interface definitions, covering nested objects, array element types, and union types. It is a fast way to turn an API response into typed code, and the inference runs entirely inside your browser.

How to use JSON to TypeScript

1Paste a representative JSON response — the more complete the fields, the more accurate the inference.
2Enter a name for the root type; the default is Root.
3Review the generated interfaces; nested objects are extracted into separate named types.
4Copy the result into your project, then mark optional fields by hand according to your API contract.

How do I do this in code?

Use the tool above for one-off work; for anything you repeat, move it into a script or your project.

Example output

interface Root {
  id: number;
  name: string;
  tags: string[];
  owner: RootOwner;
}

interface RootOwner {
  id: number;
  email: string;
}

Common errors and how to fix them

Symptom	Cause	Fix
Array elements are inferred as unknown[]	The array is empty in the sample JSON, so there is no element to infer a type from.	Use a sample that contains at least one element, or fill in the element type by hand.
A field is inferred as the null type	That field happened to be null in the sample, which reveals nothing about its real type.	Widen it to a union such as string \| null based on your API contract.

Frequently asked questions

Can I use the generated types in production code?+

Treat them as a starting point that still needs review. A single JSON sample cannot express optional fields, unions, or what a null value really means, so compare the output against your API documentation and add ? and union types where they belong. The durable answer is generating types from an OpenAPI or GraphQL schema.

What happens when a field name is not a valid identifier?+

Keys with hyphens or spaces, or keys that start with a digit, are emitted as quoted property names such as "user-id": string. That is valid TypeScript; you just have to read those properties with bracket notation.

Related tools

All tools

JSON to YAML Converter

Convert JSON to YAML while preserving the nesting

YAML to JSON Converter

Convert YAML to JSON, multi-document files included

JSON to CSV Converter

Convert a JSON array of objects to CSV, with nested fields flattened automatically

CSV to JSON Converter

Convert CSV to JSON with automatic header and delimiter handling

JSON to Go Struct

Convert JSON to Go structs with json tags filled in

JSON to Python Dataclass

Convert JSON to Python dataclasses or Pydantic models