JSON to TypeScript Interface Generator
Paste any JSON and instantly generate TypeScript interfaces with correct property types, optional fields, and nested object support. All conversion happens client-side — your data never leaves your browser.
JSON to TypeScript
Generate TypeScript interfaces or type aliases from JSON data. Handles nested objects, arrays, nulls, and mixed types.
About JSON to TypeScript
- Interfaces vs Types — interfaces are extendable and commonly used for object shapes; type aliases support unions and intersections.
- Nested objects — by default, each nested object gets its own named type. Enable "Inline nested" to embed them directly.
- Arrays — element types are inferred from all items. Mixed-type arrays become union types (e.g.,
(string | number)[]). - Root arrays — if your JSON is an array of objects, all objects are merged to produce a complete type.
- Null values — inferred as
null. Enable "Optional props" to mark all properties with?. - Everything runs in your browser — no data is sent over the network.
What are TypeScript interfaces?
TypeScript interfaces define the shape of an object by specifying property names and their types. They provide compile-time type checking without generating any JavaScript output, making them ideal for describing API response shapes, configuration objects, and data models. Interfaces can extend other interfaces and support optional properties, readonly modifiers, and index signatures.
Common use cases
Developers use JSON-to-interface generators when integrating with REST APIs, defining database model types, creating form validation schemas, and migrating JavaScript codebases to TypeScript. Pasting a sample API response and generating interfaces saves significant manual typing and reduces the chance of type errors.
Frequently Asked Questions
What is the difference between TypeScript interfaces and types?
Interfaces are best for defining object shapes and can be extended or merged through declaration merging. Type aliases are more flexible and can represent unions, intersections, and primitives. For object shapes, interfaces are generally preferred by convention.
Can this tool handle nested JSON objects?
Yes. The generator recursively processes nested objects and arrays, creating separate named interfaces for each nested structure. Array element types are also correctly inferred from the sample data.