JSON to TypeScript Generator
Generate strongly typed TypeScript interfaces and types from JSON.
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Free Online JSON to TypeScript Interface Generator
The JSON to TypeScript Interface Generator automatically converts JSON objects, arrays, and complex API responses into clean, idiomatic TypeScript definitions in real time. Eliminating tedious manual typing, it recursively detects nested structures, merges heterogeneous array models, marks missing properties as optional (key?: type), and infers union types where appropriate. Everything runs 100% in your browser without sending proprietary payload data over the internet.
1. How to Generate TypeScript Interfaces
Create typed models in three simple steps:
- Paste your API JSON response into the left editor or upload a .json file.
- Specify a custom name for your root interface (e.g., 'UserApiResponse').
- Click 'Generate Interfaces' to produce strongly-typed TypeScript code.
- Copy to clipboard or download the .ts file directly into your codebase.
2. Key Features
2.1 Smart Type Inference & Union Types
Handles heterogeneous arrays and nullable properties cleanly by creating union types (e.g. string | number).
2.2 Multi-Object Model Merging
Analyzes all objects within a list to ensure optional fields (with '?' modifiers) are correctly identified.
2.3 Syntax Highlighting & Formatting
Output is displayed with full keyword highlighting, line numbering, and clean code formatting.
3. Practical Applications & Target Audience
Generating TypeScript interfaces from real JSON payloads accelerates frontend and backend engineering:
- Frontend Engineers: Creating strong type definitions for Next.js, React, and Vue applications consuming REST or GraphQL APIs
- Backend Developers: Typing third-party webhook payloads (Stripe, GitHub, Slack) and API integration responses
- Full-Stack Teams: Maintaining end-to-end type safety between client components and JSON database records
- Node.js & Deno Developers: Generating clean DTOs (Data Transfer Objects) for NestJS, Express, or Fastify backends
4. Frequently Asked Questions (FAQ)
4.1 How does the tool determine optional properties?
When an array of objects is provided, the generator inspects every object in the collection. If a key appears in some objects but is absent in others, it is automatically marked with an optional '?' modifier.
4.2 Can I customize the root interface name?
Yes. Use the root interface name field to specify names like 'UserProfile', 'ApiResponse', or 'OrderDetails'. Nested child models will be named automatically based on their parent key.
4.3 How are null values and mixed types handled?
Properties containing null or undefined values are typed with union types (e.g., string | null). If a field contains mixed types across array items, a union like string | number is generated.
4.4 Is my proprietary API response uploaded to a server?
No. The recursive parsing and interface generation runs entirely inside your browser's JavaScript engine. Your source code and payloads remain private.
5. Useful Related Tools
- JSON Formatter – Format, beautify, and inspect JSON payloads.
- JSON Validator – Validate JSON syntax and auto-fix formatting errors.
- JSON to YAML Converter – Transform JSON to clean YAML format.