Last updated: March 2026
What Is the JSON to TypeScript Converter?
The JSON to TypeScript Converter is a free online tool that transforms any JSON object into TypeScript interfaces or type aliases — no signup, no download required. Paste a JSON API response, and get properly typed TypeScript code instantly with nested interfaces, array types, and null handling.
TypeScript adoption has grown to over 78% of JavaScript developers as of the 2025 Stack Overflow survey. One of the most common tasks when integrating APIs is converting sample JSON responses into TypeScript types — developers do this dozens of times per project. This tool focuses on the 90% use case: paste JSON, get types, copy, done.
The converter handles nested objects, arrays of objects, mixed-type arrays, null values, and optional properties. It also offers Zod schema output for runtime validation — a feature most competitors lack.
How to Use the JSON to TypeScript Converter
- Paste your JSON into the left panel (or click "Sample" to see an example)
- Set your root interface name (default: "RootObject")
- Choose interface vs type alias, and toggle export/readonly/optional as needed
- The TypeScript output generates instantly in the right panel
- Click "Copy" to copy to your clipboard, or ".ts" to download the file
- Toggle "Zod" for runtime validation schemas
Key Features
- Nested object handling. Every nested object becomes a separate, named interface. Property names are converted to PascalCase automatically. Identical shapes are deduplicated.
- Array type inference. Homogeneous arrays produce typed arrays. Mixed arrays become union types. Empty arrays default to
unknown[]. - Zod schema output. Toggle Zod to get runtime validation schemas alongside your compile-time types. Catches bad API data before it causes crashes.
- Configurable output. Interface vs type alias, export keyword, optional properties, readonly modifiers, array format, and null handling — all controllable from the options bar.
- Syntax highlighting. The output panel highlights TypeScript keywords, types, and strings for readability. Copy or download as a
.tsfile.
Frequently Asked Questions
How do I convert a JSON API response to TypeScript types?
Paste the JSON response into the left panel and the converter automatically generates TypeScript interfaces for every object and nested object. Copy the output directly into your project's types file.
What's the difference between interface and type in TypeScript?
Interfaces can be extended and merged (declaration merging), making them better for object shapes that might grow. Type aliases are more flexible for unions, intersections, and primitives. For API response types, either works — interfaces are the conventional choice.
How does this tool handle arrays in JSON?
If all array elements have the same shape, it generates one interface and types the array as InterfaceName[]. If elements have different shapes, it creates a union type. Empty arrays become unknown[].
What is Zod and why would I want Zod output?
Zod is a TypeScript-first schema validation library. While TypeScript types only exist at compile time, Zod schemas validate data at runtime — important for API responses that might not match expected types. This tool can generate both.
Can this handle deeply nested JSON with multiple levels?
Yes — the converter recursively walks any depth of nesting, generating separate named interfaces for each object level. A 5-level deep JSON object will produce 5+ interfaces with proper type references between them.