How are nested objects handled?

Each nested object generates a separate named interface, and the parent references it by name.

How are null fields treated?

Fields with null values are marked as optional (?) and typed as 'unknown'.

What happens with mixed-type arrays?

Mixed arrays produce union types, e.g., Array .

Can I use type aliases instead of interfaces?

Yes — toggle the 'Use type alias' option to generate 'type Foo = { ... }' syntax instead.

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JSON to TypeScript Interface Generator

Convert JSON objects into TypeScript interface or type alias definitions automatically.

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About this tool

Paste any JSON and instantly generate TypeScript interfaces with proper types, nested interfaces, optional fields, and array types. Supports options for interface vs type alias, JSDoc comments, and readonly modifiers to match your project's coding style.

How to use

1 Step 1: Paste your JSON object into the input area.
2 Step 2: Enter a root interface name (defaults to 'Root').
3 Step 3: Toggle options for type alias, JSDoc comments, or readonly modifier.
4 Step 4: Click Generate and copy the TypeScript output.

About this tool

How to use

Frequently Asked Questions