<iframe src="https://devtoolbox.dedyn.io/tools/typescript-type-generator" width="100%" height="700" frameborder="0" title="JSON to TypeScript Type Generator"></iframe>
JSON to TypeScript Type Generator
Paste JSON and instantly generate TypeScript interfaces, type aliases, and type guards. Handles nested objects, arrays, optional fields, union types, and more. Everything runs in your browser — your data stays private.
TypeScript types will appear here...
About JSON to TypeScript Type Generation
TypeScript's static type system catches bugs at compile time and provides powerful editor autocompletion. When working with JSON data from REST APIs, configuration files, or databases, manually writing type definitions is tedious and error-prone. This tool automates that work by analyzing your JSON structure and emitting clean, idiomatic TypeScript.
The generator recursively inspects every value in your JSON. Nested objects become separate named interfaces. Arrays are analyzed to determine element types, including union types when elements differ. Fields that appear in some objects but not others are marked optional. Null values produce nullable union types. Date-like strings are annotated with comments.
Features
Generates interface or type alias syntax
Optional export keyword on all types
Handles deeply nested objects with separate named interfaces
Detects array element types (primitives, objects, mixed/union)
Marks optional fields when array objects differ in structure
Generates runtime type guard functions
PascalCase naming derived from property keys
Optional readonly and ? modifiers
Syntax-highlighted output with one-click copy
Live conversion as you type
100% client-side — your data never leaves your browser
How does this JSON to TypeScript generator handle nested objects?▼
The generator recursively walks your entire JSON structure. Each nested object is extracted into its own named interface (or type alias), using the property key as the interface name in PascalCase. For example, a property called "shippingAddress" containing an object becomes a separate "ShippingAddress" interface. This keeps your types clean, reusable, and easy to import individually.
What are TypeScript type guards and why would I need them?▼
Type guards are runtime functions that narrow a value's type within a conditional block. When you fetch JSON from an API, TypeScript cannot verify the shape at compile time. A type guard like "isUser(data)" checks that the object actually matches your interface at runtime, giving you both compile-time safety and runtime validation. This tool generates type guard functions automatically for your root type.
Should I use interfaces or type aliases for JSON data in TypeScript?▼
Both work well for JSON structures. Interfaces are generally preferred because they can be extended with "extends", produce clearer error messages, and are the conventional choice for object shapes. Type aliases are more flexible for union types, mapped types, and conditional types. For straightforward JSON-to-TypeScript conversion, interfaces are the standard recommendation, but either approach is valid.
Is my JSON data safe when using this converter?▼
Yes, completely. This tool runs 100% in your browser using client-side JavaScript. Your JSON data never leaves your computer and nothing is sent to any server. You can verify this by checking the Network tab in your browser developer tools or by disconnecting from the internet after the page loads — the tool continues to work offline.