QQuickKit

JSON to TypeScript

Paste any JSON and instantly generate matching TypeScript interfaces, with nested object and array type inference.

About This Tool

When wiring up a backend API or debugging a data structure, developers often have to hand-write TypeScript type definitions to match a JSON response — tedious and error-prone. QuickKit's JSON to TypeScript tool recursively analyzes the JSON you paste, infers field types, and generates matching interface definitions. Nested objects become named sub-interfaces and arrays with mixed element types become union types. Everything runs locally in your browser — your data is never uploaded.

Features

  • ✓Recursive Type Inference — Analyzes nested objects and arrays, generating a matching TypeScript interface at every level.
  • ✓Array Union Types — Produces a union type when array elements have mixed types, e.g. (string | number)[].
  • ✓Named Sub-Interfaces — Nested objects are named after their field key in PascalCase, with automatic numeric suffixes for name collisions.
  • ✓Custom Root Interface Name — Set the name of the top-level interface so you can paste it directly into your project.
  • ✓Fully Client-Side — All type inference runs in your browser. Your JSON is never sent to a server.

FAQ

Why does an array field sometimes produce unknown[]?
When an array's elements span more than 5 distinct types, this tool falls back to unknown[] to avoid generating an unreadably large union type. In that case, review the raw data and adjust the type definition manually.
How are nested interface names decided?
Each nested object is named after the field key it appears under, converted to PascalCase — a userProfile field produces a UserProfile interface. If a name collides with a differently-shaped object, a numeric suffix (like Address2) is appended to disambiguate.
Can this tool handle advanced JSON Schema syntax?
No. This tool performs pure structural type inference based on actual JSON values — it doesn't support JSON Schema concepts like oneOf or format validation. It's built for the common case of pasting an API response and getting an interface back.
Can I use the generated types directly in production?
The output is a solid starting point, but you should review it against your actual business logic — mark some fields as optional, tighten union types, or replace generic strings with more precise types (like a Date type alias for date strings).

Further Reading