How do I convert JSON to TypeScript interfaces?

Paste JSON in the left panel. Nested objects are extracted into interfaces, or type aliases if you change Output. Copy or download the result. Types update as you type after a short pause.

Does this tool upload my JSON?

No conversion API is called. Conversion runs in the browser, and the request made when visiting the site does not include the JSON you paste.

Can I convert a top-level JSON array?

Yes. The converter emits an item type plus a type alias for the array.

How are null and missing properties handled?

Missing keys across array items become optional. A null value is typed as null unless Mark optional is selected, which adds ? to those fields.

When should I use type aliases instead of interfaces?

Use interfaces for extendable object shapes. Use type aliases when you prefer export type syntax, or when the root value is already an array or union.

Is the converter free?

Yes. There is no account and no usage cap on this static page.

JSON to TypeScript Converter

Convert JSON to TypeScript interfaces in your browser

Developer Tools Productivity

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Launched: Nov 1, 2026
Website: json-to-ts-interface.com
Pricing: Free
Platforms: Web

JSON to TypeScript Converter screenshot 1

JSON to TypeScript Converter generates TypeScript interfaces or type aliases from a JSON sample, such as an API response or test fixture. Paste JSON and it extracts nested objects into named types, merges arrays of objects so fields missing from some items become optional, turns mixed arrays into unions, and suggests enums for small repeated sets of strings. You can set the root type name, switch between interfaces and type aliases, choose 2- or 4-space indent, and decide whether null fields stay null or become optional. Output updates as you type and can be copied or downloaded as a .ts file. Conversion runs in the browser, and your JSON is not posted to a conversion API. Free to use.

What JSON to TypeScript Converter does

JSON to TypeScript conversion: Accepts a valid JSON object, array, or primitive and generates TypeScript definitions.
Interfaces or type aliases: Switch output between interfaces and type aliases.
Nested object inference: Extracts nested objects into named types and references them from the parent.
Array and optional-field handling: Merges arrays of objects and marks fields missing from some items as optional.
Null and mixed-array support: Types null values and represents mixed arrays as unions; null fields can be marked optional.
Copy or download output: Copy the generated code or download it as a .ts file, with 2- or 4-space indentation.

Who it's for

Developers working with API responses, fixtures, or other JSON who need TypeScript type definitions.

Why people use JSON to TypeScript Converter

Writing TypeScript interfaces or type aliases by hand from JSON is repetitive and can miss nested, optional, or mixed-value structures.

Paste a JSON sample and receive generated TypeScript definitions, with controls for interfaces versus type aliases, naming, indentation, and null handling.

The site says conversion runs in the browser and the pasted JSON is not sent to a conversion API.

Pricing

JSON to TypeScript Converter is free to use.

Platforms

JSON to TypeScript Converter runs on Web.

JSON to TypeScript Converter FAQ

How do I convert JSON to TypeScript interfaces?: Paste JSON in the left panel. Nested objects are extracted into interfaces, or type aliases if you change Output. Copy or download the result. Types update as you type after a short pause.
Does this tool upload my JSON?: No conversion API is called. Conversion runs in the browser, and the request made when visiting the site does not include the JSON you paste.
Can I convert a top-level JSON array?: Yes. The converter emits an item type plus a type alias for the array.
How are null and missing properties handled?: Missing keys across array items become optional. A null value is typed as null unless Mark optional is selected, which adds ? to those fields.
When should I use type aliases instead of interfaces?: Use interfaces for extendable object shapes. Use type aliases when you prefer export type syntax, or when the root value is already an array or union.
Is the converter free?: Yes. There is no account and no usage cap on this static page.

JSON to TypeScript Converter launched on IndieLaunch on November 1, 2026 in Developer Tools, Productivity. Visit JSON to TypeScript Converter

New to these terms? Read what Side project and Indie hacker mean.

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anderson188

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