JSON to TypeScript Type Definition

Convert JSON data to TypeScript interface type definitions automatically. Supports nested objects and array type inference.

Generation Options

What is JSON to TypeScript Tool?

JSON to TypeScript Tool is a free online tool for automatically converting JSON data to TypeScript interface type definitions. In TypeScript development, we often need to define types for JSON data. Manually writing these types is time-consuming and error-prone. This tool helps you automatically generate these types.

How to Use This Tool?

  1. Enter JSON: Paste or type the JSON data you want to convert in the left input box.
  2. Format JSON: Click the “Format” button to beautify the JSON format.
  3. Configure Options: Set options as needed (add root type, readonly properties, optional properties).
  4. Set Root Type Name: Customize the root interface name in the input field.
  5. Copy Result: Click the “Copy” button to copy the generated TypeScript code to clipboard.

Key Features

  • Automatic Type Inference: Intelligently analyze JSON data structure and automatically infer TypeScript types
  • Nested Object Support: Support multi-level nested JSON objects with automatic sub-interface generation
  • Array Type Handling: Automatically identify array element types, handle homogeneous and heterogeneous arrays
  • Configuration Options:
    • Add Root Type: Auto-generate root interface containing all properties
    • Readonly Properties: Generate readonly properties, suitable for React/Redux projects
    • Optional Properties (?): Mark all properties as optional
  • Client-side Processing: Data stays on your device, protecting code privacy

Type Inference Rules

JSON Value Inferred TypeScript Type
"text" string
123 number
true / false boolean
null null
[1, 2, 3] number[]
[{...}] Inferred element type + []
{...} Generate sub-interface
Mixed Array (type1 | type2)[]

Use Cases

  • API Response Type Definition: Quickly generate type definitions for API response JSON
  • Config File Typing: Generate types for JSON config files to ensure config correctness
  • Database Model Definition: Generate TypeScript types for database query results
  • Frontend State Management: Generate readonly type definitions for Redux/React state
  • Data Validation: Combine with libraries like Zod for runtime validation

Frequently Asked Questions (FAQ)

Is this tool safe?

Absolutely safe. This tool runs entirely in your browser (client-side processing). Your JSON data is not uploaded to any server.

Does it support nested JSON?

Yes. This tool can handle JSON data with arbitrary nesting depth and automatically generate sub-interface definitions for each nested object.

How does it handle homogeneous and heterogeneous arrays?

  • Homogeneous Array [1, 2, 3] → number[]
  • Heterogeneous Array [1, "text"] → (number | string)[]

What is the readonly option for?

Checking the readonly option adds the readonly modifier to all properties in the generated type definition. In TypeScript, this means properties are read-only and cannot be reassigned. It’s suitable for:

  • React component props types
  • Redux store state types
  • Immutable data (Immutable.js) type definitions