Model an API response
Create initial TypeScript interfaces while integrating a REST, webhook or third-party API.
100% local · files never leave your browser
Generate tool
JSON to TypeScript
Generate TypeScript interfaces from sample JSON locally in your browser. Review inferred optional fields and unions before use.
✓ Free to use✓ No signup✓ Runs locally
160 bytes · local only
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Processed entirely in this tab
Your input and result are not sent to JSON Hearth or stored on a server.
When to use it
What TypeScript Types helps you do
Type generation creates a starting model from example data, reducing repetitive typing while leaving application-specific decisions to you.
Build typed fixtures
Turn representative JSON into reusable types for tests and frontend development.
Document nested payloads
Expose object and array relationships in a form familiar to TypeScript developers.
Important limitations
What to check before using the result
- A sample cannot reliably reveal optional properties, all union members or nullable fields.
- Review names and types before treating generated interfaces as a stable contract.
Common questions
About TypeScript Types
Can generated TypeScript detect optional properties?
Not reliably from one example. Optionality requires knowledge of other valid payloads or an external contract.
Should generated interfaces replace a JSON Schema?
TypeScript types help at development time, while JSON Schema can validate runtime data. They solve related but different problems.