JSON to TypeScript
FreeGenerate TypeScript interfaces from JSON objects automatically. Handles nested objects and arrays.
Why Generate TypeScript Interfaces from JSON?
When working with external APIs, you often receive JSON responses with complex, nested structures. Manually writing TypeScript interfaces for these responses is tedious and error-prone. This tool automates the process — paste the API response JSON, and get ready-to-use TypeScript interfaces instantly.
How to Use the Output
- Paste your JSON response (from an API, mock data, or fixture)
- Set the root interface name to match your data (e.g., User, Product, ApiResponse)
- Click Generate TypeScript
- Copy the output and paste it into your .ts or .d.ts file
- Review and adjust optional fields (add ? for nullable properties)
Frequently Asked Questions
What TypeScript features does this generator support?
The generator produces TypeScript interfaces with primitive types (string, number, boolean, null), nested object interfaces, typed arrays, and union types for arrays with mixed element types.
Does it handle nested objects?
Yes. Nested objects are converted into separate named interfaces. The root interface name is configurable, and nested interface names are derived from their property key names.
What if my JSON has null values?
Null values are typed as null. In production code, you may want to update these to string | null or number | null depending on what the field can actually contain.
Can I use this with API responses?
Yes. Paste the JSON response from your API into the input, set the root interface name to match your response type (e.g., UserResponse), and click Generate. The output can be copied directly into your TypeScript project.
Should I use interface or type in TypeScript?
This tool generates interface declarations. Interfaces are the recommended way to define object shapes in TypeScript because they are extensible, produce clearer error messages, and support declaration merging. For union types or computed types, use type aliases instead.