JSON to TypeScript

// HOW TO USE

1. 01Paste a sample JSON response — the cleaner the sample, the tighter the inferred types.
2. 02Set a Root name and pick interface or type.
3. 03Mixed-type arrays produce union types; nested objects become separate interfaces with names derived from the parent key.

// WHEN TO USE

Use this when integrating with a new API and needing TypeScript interfaces for the response shape, or when a backend team shares a sample payload but no formal type definitions. Generate a draft in seconds, then tighten nullable fields and union types manually before committing them. Also use it to detect contract drift: generate types from the actual response and compare the structure against committed interfaces to find fields that changed type or were added or removed.

// WHAT BUGS THIS FINDS

• Optional field typed as required

  A field absent in some responses is inferred as required from the single sample — the generated interface causes a TypeScript compile error when the API omits it. Review and add ? to nullable or conditional fields.

• Mixed-type array inferred as single type

  An array containing strings in the sample but numbers in other responses is typed as string[] — the generated type masks a real polymorphism bug the API has. Compare against multiple response samples before committing.

• Numeric ID typed as number

  An ID that is always numeric in the sample gets typed as number, but the API returns it as a string in some contexts — the generated type exposes the inconsistency before it causes a runtime parse failure.

• Type drift after API version bump

  A backend field is renamed or retyped in a new version — generate types from the new response and diff against the committed interface to surface every breaking change before the frontend integrates it.

// QA USE CASES