What this tool generates

Each JSON object becomes a TypeScript interface. Nested objects get their own named interface. Arrays of objects merge all encountered keys — keys absent from some items become optional properties. Primitive arrays produce typed array signatures like string[] or number[].

JSON to TypeScript Online

input.json

{
  "id": 1,
  "name": "Alice Johnson",
  "email": "alice@example.com",
  "age": 30,
  "active": true,
  "address": {
    "street": "123 Main St",
    "city": "New York",
    "zip": "10001"
  },
  "tags": ["admin", "editor"],
  "orders": [
    { "id": 101, "total": 49.99, "status": "shipped" },
    { "id": 102, "total": 99.00, "status": "pending" }
  ]
}

types.ts

Click Convert to generate TypeScript interfaces.

Guides for TS Types

All guides →

Guide

Repair LLM JSON Output: Handling Almost-JSON from AI

LLMs frequently return JSON wrapped in ```json fences, with single quotes, Python literals, or unquoted keys. Repair the syntax, validate strictly, then derive TypeScript types from the cleaned output.

Guide

Repair LLM JSON Output

AI responses often look like JSON but include markdown fences, comments, Python-style literals, or JavaScript object syntax.

Guide

JSON vs JS Object Literal: The Key Differences

JSON looks like a JavaScript object literal, but it is a smaller data format with stricter syntax and no executable values.

How JSON to TypeScript conversion works

Each JSON object becomes a TypeScript interface. The root object is named Root by default. Nested objects get their own named interface derived from the property key — a key named address produces an Address interface.

Arrays and optional fields

Arrays of objects merge all encountered keys across every element. If a key is absent from some items, it becomes an optional property (key?: Type). Arrays of primitives produce typed signatures like string[] or number[].

When to use this

API integration — paste a response body and get instant type definitions to paste into your TypeScript project
Prototyping — quickly scaffold interfaces when exploring a new API or dataset before writing any parsing code
Code review — verify the shape of a JSON payload matches the interfaces your code expects