JSON to TypeScript Interface Generator
Generate TypeScript interfaces from JSON with nested objects, arrays, nullable handling, and copy-ready output — all client-side.
No uploads. Everything runs locally in your browser.
Example loaded. Click Generate to create TypeScript interfaces.
Parses JSON client-side, infers nested types, and generates stable interface names.
What is this tool
Convert JSON to TypeScript interfaces instantly. Paste JSON, set the root name, choose null handling, and get clean interfaces for nested objects and arrays with copy-ready output.
Use cases
- Generate TypeScript interfaces from API responses or fixtures.
- Document data contracts for frontend and backend collaboration.
- Bootstrap typings for SDKs or client libraries.
- Quickly inspect JSON structure and nullable fields.
- Copy interfaces into editors without manual typing.
Popular ways to use this tool
- Turn API JSON responses into TypeScript contracts for frontend apps.
- Generate interfaces for mock data and testing fixtures.
- Share inferred models with teammates in PRs or docs.
- Explore nested JSON quickly without writing manual types.
- Toggle null handling to match your project’s typing style.
How to use
- Paste your JSON object or array.
- Set the root interface name and choose null handling (union vs optional).
- Click Generate to build interfaces, then copy the output.
- Use Fill example or Clear to reset and run another conversion.
Features
- Parses JSON objects and arrays with nested structures
- Infers string, number, boolean, null, arrays, and objects
- Null handling toggle: union null or optional fields
- Auto-generated nested interface names with deduplication
- Copy output, example fill, and clear/reset controls
FAQ
How are types inferred?
We inspect values to infer primitives, arrays, and objects. Nulls can be unioned with null or marked optional based on your setting.
Do you support nested objects and arrays?
Yes. The generator creates additional interfaces for nested objects and infers array item types.
What happens with null values?
Choose union (type | null) or optional fields. Optional marks the property with ? and uses 'any' as the type for null-only fields.
Is my JSON sent anywhere?
No. Everything runs locally in your browser.
Can I rename the root interface?
Yes. Set the root name input before generating and it will be used for the top-level interface.