JSON to TypeScript Interface Generator
Convert raw JSON payloads or API responses into clean, strictly-typed TypeScript interfaces, nested object types, and optional array item definitions.
How to Use JSON to TypeScript Interface Generator
- Paste any valid JSON object, array, or REST API response into the input editor.
- Enter your desired PascalCase root TypeScript interface name (e.g., ApiResponse).
- Click Process to infer nested interfaces, optional properties, and union array types.
- Copy the generated TypeScript definitions directly into your .ts or .d.ts file.
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Frequently Asked Questions
How does the JSON to TypeScript Interface Generator infer nested object types?
The generator parses your raw JSON payload into an Abstract Syntax Tree (AST) and recursively traverses every object property. Nested child objects are extracted into standalone PascalCase interfaces (such as ApiResponse_Author) and referenced by the parent interface for clean, modular TypeScript definitions.
How are arrays of objects with optional or inconsistent keys handled?
When an array contains multiple JSON objects, our inference engine inspects every object in the array, merges the union of all discovered property keys, and automatically marks keys that do not appear in every element with TypeScript's optional modifier ('?').
How does the generator handle null values and heterogeneous arrays?
Explicit null values are typed as 'any | null' so strictNullChecks compilers flag nullable fields. Arrays containing mixed primitive types (such as strings and numbers) are inferred as union array types like '(string | number)[]'.
What happens if a JSON property key contains hyphens, spaces, or starts with a number?
The generator validates every property key against ECMAScript identifier rules. Keys that are not valid bare identifiers (such as 'content-type' or '2fa_enabled') are automatically wrapped in double quotes inside the generated interface so TypeScript compiles without syntax errors.
Are my proprietary API payloads or JSON schemas uploaded to any external server?
No. All JSON parsing and TypeScript interface generation runs 100% locally in your web browser memory. Your proprietary API responses, auth payloads, and database schemas never leave your device.