# JSON to TypeScript Converter: Convert JSON to TypeScript interfaces in your browser

> 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.

Canonical: https://indielaunch.dev/products/json-to-typescript-converter
Last updated: 2026-11-01

|  | JSON to TypeScript Converter |
| --- | --- |
| Website | https://json-to-ts-interface.com/ |
| Pricing | Free |
| Platforms | Web |
| Categories | Developer Tools, Productivity |
| Based in | United States |
| Launched | 2026-11-01 |
| Made by | anderson188 |

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.

## Features

- **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.

## 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.

Tags: TypeScript, JSON, Code generation

## Related

- [DropLink: Share files by link without requiring the recipient to install an app](https://indielaunch.dev/products/droplink)
- [ToolCabana: 450+ free online tools, no sign-up needed](https://indielaunch.dev/products/toolcabana)
- [PageUtil: Free browser tools for documents, data, development, and everyday tasks](https://indielaunch.dev/products/pageutil)
- [ZIPZAX: 425 free online tools for everyday digital work](https://indielaunch.dev/products/zipzax)
- [RoyaleTools: Free Clash Royale deck finder, War builder & minigames](https://indielaunch.dev/products/royaletools)
- [More Developer Tools](https://indielaunch.dev/categories/developer-tools)
- [More Productivity](https://indielaunch.dev/categories/productivity)
- [anderson188 on IndieLaunch](https://indielaunch.dev/u/anderson188)