JSON to TypeScript
Paste JSON and get strict TypeScript types—ideal for Next.js API responses and config objects.
When to use this tool
- Deriving TypeScript types for a REST or GraphQL response you do not own.
- Generating initial types from a config or fixture JSON.
- Teaching — showing juniors how optional fields emerge from nullable data.
How it works
- Paste a representative JSON sample (keep it small but include every field variant).
- Choose strict or loose mode if the UI offers it.
- Copy the generated interfaces into your codebase.
- Tighten types by hand where the generator guessed unions or records.
Privacy: This tool runs entirely in your browser. Your input is not sent to our servers.
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Frequently asked questions
Does it infer discriminated unions?
Not automatically. Combine multiple payload shapes by hand with a shared discriminant field like `type` or `kind`.
Does the output include runtime validation?
No. Pair the types with a runtime validator like zod or valibot if the API boundary is untrusted.
Will nested arrays be typed correctly?
Yes, as long as array elements share a shape. Mixed-shape arrays are inferred as unions and may need manual tightening.