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JSON to TypeScript Converter

Generate TypeScript interfaces and types from JSON data instantly.

Root type name

Interfaces(off = type aliases)Optional for nullsExport types

JSON Input

TypeScript Output

TypeScript types will appear here...

All conversion happens in your browser. No data is sent to any server.

About JSON to TypeScript Converter

Free online JSON to TypeScript converter that generates accurate TypeScript interfaces or type aliases from any JSON input. Handles nested objects, arrays, nullable values, and mixed-type arrays. Customize the root type name, choose between interfaces and type aliases, toggle optional properties for nulls, and add export keywords. Auto-converts on valid JSON input with a live preview. 100% browser-based, no signup required.

Frequently Asked Questions

How does the JSON to TypeScript converter work?▾

Paste valid JSON into the input field and the tool instantly generates corresponding TypeScript interfaces or type aliases. It analyzes the structure, infers types for each value (string, number, boolean, null), and creates named interfaces for nested objects and arrays.

Does it handle nested objects and arrays?▾

Yes. Nested objects are converted to separate named interfaces (using PascalCase based on the parent key name). Arrays of objects are analyzed to produce a single interface that merges all keys found across array elements, with union types where values differ.

Can I generate type aliases instead of interfaces?▾

Yes. Toggle the 'Type Aliases' option to generate 'type' declarations instead of 'interface' declarations. Both produce valid TypeScript — interfaces are generally preferred for object shapes as they support declaration merging, while type aliases are more flexible for unions and intersections.

How are null values handled?▾

By default, null values are typed as 'null'. With the 'Optional for nulls' toggle enabled, fields with null values become optional properties (using the '?' modifier) instead, which is often more practical for API response types where null indicates a missing value.

Can I use this for API response typing?▾

Absolutely. Copy a JSON response from your browser's Network tab or API client, paste it into the converter, and get ready-to-use TypeScript types. This is one of the most common use cases — it saves significant time compared to manually writing types for complex API responses.

Is this tool free and private?▾

Yes, completely free with no signup. All conversion happens in your browser — your JSON data is never sent to any server.