JSON to TypeScript Generator

Turn a JSON sample into TypeScript interfaces with nested objects, arrays, optional fields, and primitive types inferred locally.

input.json
types.ts
Click Convert to generate TypeScript interfaces.

Related

Guides for TS Types

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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