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JSON to TypeScript Types Online

Convert JSON into TypeScript interfaces, type aliases or a Zod schema live, with real optional-field detection across arrays.

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Result

This page opens the converter with type alias preselected as the output format — paste a JSON object or array and it prints type Name = { ... }; blocks instead of interfaces, useful when your codebase's style guide favors type over interface.

The inference underneath is identical to the interface mode: nested objects become their own named type, arrays of objects are compared item by item so a field missing from some entries is marked optional, and a field that mixes null with a real value comes out as a union like count: number | null.

Switch to interface syntax or a Zod schema from the same pasted JSON at any time — only the printed syntax changes, the detected shape stays the same.

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Executed in Browser

Your files and inputs never leave this device. Processing runs completely offline. 100% Secure.

Accepted Formats & Rules

  • Recursively infers a named interface for every nested object and every array of objects.
  • Merges array element shapes field by field, so a field only present in some items becomes optional.
  • Live conversion on every keystroke, with invalid JSON reported inline instead of crashing the page.

Key Benefits

✓ 100% Offline: your JSON payload and the generated types never leave this device.
✓ Real optional-field detection: comparing every object in an array and marking fields missing from some of them as optional, not a guess.
✓ Three output formats from one inference engine: TypeScript interface, type alias, or a ready-to-paste Zod schema.

Use Cases

  • • Paste a REST or GraphQL API response and get typed interfaces for it in seconds, instead of hand-writing them field by field and missing an optional one.
  • • Check whether a field your frontend relies on is actually present on every record: paste an array of sample records and see which fields the tool marks optional (?) because some items lack them.
  • • Generate a Zod schema straight from a sample payload to validate untrusted JSON (webhooks, third-party APIs, user uploads) at runtime, not just at compile time.