JSON to TypeScript Interface Generator

Generating TypeScript Types from JSON

Writing TypeScript interfaces for API responses by hand is tedious and error-prone, especially for deeply nested objects. Our tool takes a JSON sample and infers TypeScript interface definitions automatically — arrays become typed arrays, nested objects become sub-interfaces, and primitive values map to their TypeScript equivalents (string, number, boolean, null).

Paste a real response from the API you're integrating, and get typed interfaces in seconds. This speeds up integration work significantly — you go from raw JSON to type-safe code without manual interface authoring. The generated types reflect the actual shape of the data, not what the documentation says (which is often out of date).

Generated types are a starting point: you may want to rename types for clarity, add union types for polymorphic fields, mark optional properties with ?, or add documentation comments. But the structural scaffolding is done for you, saving the most tedious part.

Tips

• If a field is sometimes null and sometimes a value, add | null to the type: name: string | null.
• Optional vs nullable: name?: string means the key may not exist; name: string | null means it exists but may be null.
• For arrays with mixed types, TypeScript uses union arrays: (string | number)[].
• Use interface for object types you extend, and type for unions and aliases — both work for JSON shapes.