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KioTools
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JSON to TypeScript

What is this tool?

A JSON-to-TypeScript type generator. It walks the parsed JSON, names an interface for each object shape, de-duplicates identical shapes, and infers array element types — a fast 'paste JSON, get types' helper rather than a full JSON Schema compiler.

When to use it

  • Typing an API response you're integrating against
  • Bootstrapping model types from a sample payload
  • Checking what shape a config or fixture file actually has
  • Turning a JSON example in documentation into usable types
  • Getting a starting point for types you'll then refine by hand

How to use it

  1. 1Paste a JSON object or array
  2. 2Optionally rename the root interface
  3. 3Read the generated interfaces in the output panel
  4. 4Copy them into your project
  5. 5Adjust nullable fields and unions manually where the sample was incomplete

Frequently asked questions

How are null values handled?

A field that is null in the sample is typed as null and marked optional, since the sample doesn't show its real type.

What about arrays with mixed types?

The element types are unioned — for example an array of numbers and strings becomes (number | string)[].

Does it detect enums or date strings?

No — strings are typed as string. Narrowing to literal unions or branded types is left to you.

Is the JSON sent anywhere?

No — type generation runs entirely in your browser.