🔄 JSON to TypeScript Interface Generator

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TypeScript interfaces generated successfully!
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ℹ️ About JSON to TypeScript Interface Generator

JSON to TypeScript Interface Generator turns a valid JSON sample into TypeScript declarations you can paste into an API client, frontend model, test fixture, or shared DTO file. JSON is a language-neutral data interchange syntax defined by RFC 8259 and ECMA-404; this tool maps its objects, arrays, strings, numbers, booleans, and nulls into TypeScript object types and interfaces.

Practical uses:

  • Generate a first-pass interface from a REST or GraphQL JSON response.
  • Document the shape of configuration files, webhook payloads, fixtures, and mock API data.
  • Migrate JavaScript objects into TypeScript with named interfaces, exported declarations, and readonly properties.
  • Compare incoming JSON with the generated type analysis before writing stricter validation rules.

Generated type behavior:

  • Object properties become TypeScript interface fields using the selected root interface name.
  • Nested object properties produce nested interfaces; arrays are inferred from observed element types.
  • Mixed arrays can generate union element types such as (string | number)[].
  • With strict null checks enabled, JSON null stays explicit instead of being widened to any.
  • The optional-properties option can mark every generated field with ? for partial payloads and PATCH-style updates.

Example: {"id":1,"name":"Ada","active":true} can become export interface User { id: number; name: string; active: boolean; }. After generation, rename interfaces and refine fields for domain rules such as IDs, ISO date strings, enum-like values, or nullable API states.

Limitations:

  • The output is inferred from the sample, not from a complete schema or every possible production payload.
  • JSON has no native Date, bigint, undefined, comments, functions, or cyclic references, so those require manual TypeScript decisions.
  • Arrays of objects and empty arrays may need hand refinement when real data contains additional fields or variants.
  • Generated interfaces describe compile-time structure only; use a validator or JSON Schema when you need runtime enforcement.

References: JSON syntax and interoperability are covered by RFC 8259 and ECMA-404. TypeScript interface and object-type behavior is documented in the TypeScript Handbook on object types, with null handling described in the strictNullChecks TSConfig reference.

API Usage Example:

POST /api/tools/webdev/json-to-typescript
Content-Type: application/json

{
    "json": "{\"id\":1,\"name\":\"Ada\",\"active\":true}",
    "rootInterfaceName": "RootInterface",
    "namingStyle": "PascalCase",
    "optional": false,
    "exportInterfaces": true,
    "readonly": false,
    "strictNullChecks": true
}
Ready