🔄 JSON to TypeScript Generator — Interface, Type & Readonly Builder
Convert JSON into TypeScript Interface, TypeScript Type, TypeScript Readonly Interface, or TypeScript Enum classes instantly. 100% client-side — your data never leaves your browser.
📋 When to Use the JSON to TypeScript Generator
TypeScript developers use this generator to instantly create interfaces and type aliases from JSON responses — paste an API response, get typed definitions in seconds. Frontend engineers working with REST APIs or GraphQL convert raw JSON into strict TypeScript types for better autocomplete and compile-time safety. Full-stack developers use the optional mode to mark nullable API fields with ?, and the camelCase option to convert snake_case JSON keys to idiomatic TypeScript. Nested objects automatically become nested interfaces, arrays of objects get their own type. All processing runs client-side — your JSON never leaves your browser.
⚙️ How the JSON to TypeScript Generator Works
Your JSON is parsed with JSON.parse() in the browser. The generator walks the object tree recursively: primitive values map to their TypeScript equivalents (string, number, boolean), null maps to any (or ?: any with optional mode), empty objects {} become Record<string, unknown>, and arrays are inferred by sampling elements — homogeneous arrays get typed (string[], number[]), empty/mixed arrays fall back to any[], and arrays of objects generate a nested type from the first element. Nested objects produce separate interfaces/types with PascalCase names derived from the field key (collision-safe with numeric suffixes). Three output modes: export interface (standard), export type = { } (type alias), and readonly interface (immutable). All computation is browser-side — nothing is sent to any server.
How to Use the JSON to TypeScript Generator
- Paste your JSON — Drop any valid JSON object into the input panel. Nested objects, arrays, and the special
_classNamekey (to name the root type) are fully supported. - Choose your output mode — Select Interface (standard), Type Alias, or Readonly Interface from the dropdown.
- Configure options — Toggle optional fields (mark null as
?), camelCase conversion for snake_case keys, or tab indentation. - Generate and copy — Click Generate to produce clean, idiomatic TypeScript. Copy it directly into your IDE or
.d.tsfile.
Frequently Asked Questions
What languages does this support?
This generator produces native TypeScript in three modes: Interface (export interface Foo { ... }), Type Alias (export type Foo = { ... }), and Readonly Interface (all fields prefixed with readonly). No Java, C#, or Lombok — pure TypeScript.
Can it handle nested JSON objects?
Yes! Nested objects are automatically converted to inner/nested classes, preserving the full object hierarchy in every target language.
What's the difference between TypeScript Type and TypeScript Readonly Interface?
Interface (export interface) is the standard TypeScript approach — supports declaration merging and is preferred for public APIs. Type Alias (export type = { }) is more concise for inline types and unions. Readonly Interface adds the readonly modifier to every field, preventing reassignment after construction — ideal for immutable data transfer objects.
How does the optional field option work?
When enabled, any field where the JSON value is null or the key is absent will be marked with ? (e.g., middleName?: string). This tells TypeScript the field may be undefined at runtime — safer for API responses where fields are conditionally present.
How does camelCase conversion work?
Enable the camelCase option to convert snake_case JSON keys (first_name) to idiomatic TypeScript (firstName). Already-camelCase keys are preserved. This follows the standard TypeScript/JavaScript naming convention.
Is my JSON data safe?
Absolutely. Everything runs in your browser using JavaScript — your JSON is parsed with JSON.parse() and the TypeScript code is generated client-side. No server-side processing, no API calls, no data logging.