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JSON to TypeScript - Convert JSON to TS Interfaces Online Free

Free JSON to TypeScript converter. Generate TypeScript interfaces and types from JSON data instantly. Handles nested objects, arrays, and optional properties.

About JSON to TypeScript Conversion

Converting JSON data to TypeScript interfaces is one of the most common tasks in modern web development. TypeScript's type system helps catch errors at compile time and improves code quality through better IDE support and auto-completion. Manually writing interfaces for complex JSON structures is tedious and error-prone. This tool automates the process by analyzing your JSON data and generating accurate TypeScript interfaces. It handles nested objects by creating separate named interfaces, correctly types arrays (including mixed-type arrays as union types), and treats null values appropriately. You can customize the root interface name, toggle the export keyword, and add readonly modifiers. All conversion happens locally in your browser โ€” your JSON data is never sent to any server.

Frequently Asked Questions

Why convert JSON to TypeScript?
Converting JSON to TypeScript interfaces provides type safety, IDE autocompletion, and compile-time error checking. Instead of treating data as any, TypeScript ensures you use the correct properties and types, preventing runtime errors and improving code quality.
When should I use interface vs type?
This tool generates interfaces by default. Use interfaces for object shapes (they're better for OOP patterns and declaration merging). Use type for unions, primitives, and more functional approaches. For JSON conversion, interfaces are preferred.
How do nested objects get converted?
This tool generates separate interfaces for each nested object. For example, if your JSON has a user: { name, email }, it creates a User interface and a Root interface that uses it. This keeps types clean and reusable.
How are optional properties handled?
This tool marks all properties as required by default. If you need optional properties (marked with ?), you should manually add them or use the readonly checkbox to add that modifier. See JSON Formatter to validate your JSON structure first.
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How to Use

  1. Paste your JSON data into the input panel
  2. Set the root interface name (default: Root)
  3. Toggle export and readonly options as needed
  4. Click Convert and copy the generated TypeScript interfaces

Common Use Cases

  • Generating TypeScript interfaces from API response data
  • Creating type definitions for configuration files
  • Building typed models from database JSON exports
  • Quickly scaffolding types for new TypeScript projects

Frequently Asked Questions

How do I convert JSON to TypeScript interfaces?
Paste your JSON data into the left panel, optionally set a root interface name, and click Convert. The tool will generate TypeScript interfaces with proper types for all fields.
Does it handle nested JSON objects?
Yes. Nested objects are converted to separate named interfaces. For example, an 'address' field containing an object will generate both a Root interface and an Address interface.
How are arrays typed in the output?
Homogeneous arrays (all same type) are typed as Type[]. Mixed arrays are typed as union types like (string | number)[]. Empty arrays become unknown[].
Can I use the generated types in my project?
Yes. Copy the output and paste it directly into a .ts or .d.ts file. The generated interfaces are valid TypeScript and ready for production use.
Is my JSON data safe?
Absolutely. All processing happens locally in your browser using JavaScript. Your data never leaves your device โ€” no server requests are made.