JSON to TypeScript

LOCAL · Browser-Only

Convert JSON data to TypeScript interfaces and types

Ctrl+Enter to convert

Input JSON

TypeScript Output

TypeScript types will appear here

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What is JSON to TypeScript?

Free online JSON to TypeScript converter: paste any JSON object and instantly generate accurate TypeScript interfaces and type definitions.

The tool analyzes the structure of your data, infers a type for each field, and handles nested objects, arrays, optional fields, and union types for mixed arrays. Turn an API response into typed interfaces, generate types from a fetch result, or convert a config file into a data model without writing the boilerplate by hand. Set a custom root interface name and copy the output straight into your project. All processing happens in your browser, so your JSON, including private API payloads, stays on your device. No signup required.

How to Use JSON to TypeScript

1Paste your JSON data into the input editor
2Optionally set a custom root interface name
3Click 'Convert' to generate TypeScript interfaces
4Copy the generated TypeScript code and paste it into your project

Frequently Asked Questions

How does JSON to TypeScript conversion work?

The tool parses your JSON data and recursively analyzes each property's value to infer its TypeScript type. Strings become 'string', numbers become 'number', booleans become 'boolean', null becomes 'null', arrays become typed arrays, and nested objects generate separate named interfaces.

Does it handle nested objects and arrays?

Yes. Nested objects are extracted into separate named interfaces with proper references. Arrays are analyzed to determine the type of their elements. If array elements have mixed types, a union type is generated. Deeply nested structures are fully supported.

Can I customize the generated interface names?

Yes. You can set a custom root interface name (default is 'Root'). Nested object interfaces are automatically named based on their property key in PascalCase. You can edit the output freely after generation.

Is my JSON data safe?

Absolutely. All parsing and type generation happens locally in your browser using JavaScript. Your JSON data - including API responses, credentials, or proprietary schemas - is never transmitted to any server.

How do I generate TypeScript types from an API response?

Copy a sample JSON response from your API, paste it into the input, and the tool generates matching interfaces with the right field types. Use a representative response that includes optional or nullable fields so the generated types reflect what the API can actually return.

How are optional or null fields handled?

A field whose value is null is typed as null, and you can mark fields optional with a question mark after editing. For the most accurate types, paste a response where optional fields are present, since the generator infers types from the exact JSON you provide.

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Keep reading: TypeScript Cheat Sheet and http status codes reference. Doing this in code instead? See the JSON and data endpoints.

What is JSON to TypeScript?

Free online JSON to TypeScript converter: paste any JSON object and instantly generate accurate TypeScript interfaces and type definitions.