JSON to TypeScript

What is JSON to TypeScript?

JSON to TypeScript converts JSON objects into TypeScript interface definitions with proper type inference for strings, numbers, booleans, null, arrays, and nested objects. It generates named interfaces for nested structures, handles optional properties by detecting inconsistencies across array elements, and supports union types when a field contains mixed types. The tool produces clean, idiomatic TypeScript ready for production use.

TypeScript developers typing API responses, full-stack engineers generating shared type definitions, and frontend developers building type-safe data layers. The tool runs entirely in your browser — your data never leaves your device.

How to Use JSON to TypeScript

1. Paste a sample JSON object or array into the input editor
2. Set the root interface name — it becomes the exported type name
3. Review the generated TypeScript interfaces with proper nesting and type annotations
4. Toggle options for optional properties, readonly modifiers, and type aliases versus interfaces
5. Copy the TypeScript definitions to your project's type definition files

Common Use Cases

• Generating TypeScript interfaces from API response samples to type-check fetch calls
• Creating type definitions for JSON configuration files used in TypeScript projects
• Reverse-engineering TypeScript types from database query results for ORM integration
• Generating interfaces from third-party API documentation examples
• Creating type-safe data models from JSON Schema examples during API client development

Pro Tips

• Provide multiple JSON examples (an array of objects) so the tool can detect optional fields — a property missing in some objects becomes optional (?) in the interface
• Review generated number types carefully — some numeric IDs should be typed as string if they can have leading zeros or exceed Number.MAX_SAFE_INTEGER
• Use the interface output for object shapes and type aliases for union types — this follows TypeScript community conventions and makes your types more readable

Why Use This Tool?

• Privacy-first: All processing happens locally in your browser. No data is transmitted to any server.
• No installation required: Works in any modern browser on desktop or mobile.
• Completely free: No account, no credit card, no usage caps.
• Fast and reliable: Powered by modern Web APIs for near-instant results.

Related Concepts

Learn more about related topics: TypeScript interfaces, Type inference, Generic types, Zod schema.

Frequently Asked Questions