JSON to TypeScript Type Alias Generator
Transform JSON data into TypeScript type aliases with proper typing for nested objects, arrays, and nullable fields. All conversion runs locally in your browser — your data stays private.
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 type aliases?
TypeScript type aliases use the 'type' keyword to create named types for any shape of data — objects, unions, intersections, tuples, and primitives. Unlike interfaces, type aliases can represent non-object types like string | number unions and mapped types. They are resolved at compile time and produce no runtime JavaScript.
Common use cases
Type aliases are preferred when you need union types (e.g., Status = 'active' | 'inactive'), computed or mapped types, or when working with functional programming patterns. They are also common in libraries that export complex generic types and in projects that consistently use 'type' over 'interface' by convention.
Frequently Asked Questions
When should I use type aliases instead of interfaces?
Use type aliases when you need union or intersection types, mapped types, or when your team's style guide prefers them. If you only need to describe an object shape and may want declaration merging, interfaces are the conventional choice.
Are TypeScript type aliases the same as interfaces at runtime?
Both are completely erased at compile time and produce no JavaScript output. At runtime, there is zero difference. The choice between them is purely a compile-time and developer-experience decision.
Related Convert Tools
TOML ↔ JSON/YAML
Convert between TOML, JSON, and YAML — perfect for Cargo.toml and pyproject.toml
Encode / Decode Multi-Tool
Base64, Base32, Hex, Binary, URL, and HTML encoding & decoding all in one tool
Base64 Codec
Encode and decode Base64 strings with Unicode support
Color Converter
Convert colors between HEX, RGB, and HSL formats