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JSON to TypeScript Converter

Paste JSON, get TypeScript interfaces instantly. 100% in your browser — data never leaves the page. interface or type, nested objects, arrays, optional fields. Free, no sign-up.

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Verified against real-world API payloads and TypeScript compiler output. — Go Tools Team · Jun 1, 2026

What is JSON to TypeScript conversion?

JSON to TypeScript conversion reads a JSON value and generates matching TypeScript interface or type definitions — eliminating hand-written boilerplate for API responses and config files. Paste a payload and get production-ready types in seconds, fully typed for nested objects, arrays, and optional fields.

Examples

API response

{"id":101,"name":"Ada Lovelace","email":"ada@example.com","active":true,"roles":["admin","user"]}

Turn a typical REST API user payload into a typed interface you can drop into your client.

Nested objects

{"order":{"id":"A-1","total":42.5,"customer":{"name":"Sam","vip":false}}}

Nested objects become separate, named interfaces (Order, Customer) referenced by field.

Array of objects (optional fields)

{"users":[{"id":1,"nick":"x"},{"id":2}]}

Keys missing from some array items are inferred as optional (nick?: string).

Mixed and null values

{"tags":["a","b"],"score":null,"meta":[1,"two"]}

Null values and mixed arrays are typed honestly (null, (string | number)[]).

GitHub-style payload

{"login":"octocat","id":1,"public_repos":2,"plan":{"name":"pro","private_repos":50}}

Snake_case keys are kept verbatim; nested plan becomes its own interface.

How to convert JSON to TypeScript

  1. 1

    Paste your JSON

    Drop a JSON object, array, or API response into the input box. Conversion starts instantly.

  2. 2

    Tune the output

    Pick interface or type, set a root name, toggle export, and choose ?: or | null for optional fields.

  3. 3

    Copy or download

    Grab the generated TypeScript with one click and paste it straight into your codebase.

How the conversion works

Structural inference
Each object becomes a named interface; identical shapes are deduplicated so you get one type, not copies.
Array merging
Arrays of objects are merged key-by-key; keys absent from some items are marked optional.
100% client-side
Parsing and generation run in your browser with no network calls, so your data stays private.

Tips for clean TypeScript types

Name your root type
Set a meaningful root name (e.g. User, ApiResponse) instead of the default Root for readable code.
Prefer optional over null when data is sparse
Use ?: for fields that may be absent and | null only when the API explicitly returns null.

Frequently asked questions

How do I convert JSON to a TypeScript interface?
Paste your JSON into the input box. The converter reads it instantly in your browser and generates a TypeScript interface on the right. Click Copy to grab the result — no upload, no account.
Should I use `type` or `interface` for JSON data?
Both work. `interface` is conventional for object shapes and gives slightly better editor errors; `type` is handy for unions and intersections. Use the Output toggle to switch between them and keep whichever your codebase prefers.
How are nested objects and arrays handled?
Nested objects become separate, named interfaces (e.g. an `address` field yields an `Address` interface). Arrays of objects are merged into one element interface; primitive arrays become typed arrays like `string[]`.
How are optional and null fields handled?
When a key is present in some array items but not others, it is marked optional. Choose `?:` (optional) or `| null` (explicit nullable) with the Optional fields toggle. Literal null values are typed as `null`.
How do I generate TypeScript types from JSON automatically in VSCode?
You can install an extension, but you don't have to. This tool runs entirely in your browser — paste, copy, done — with no plugin to install, configure, or keep updated.
Is my JSON data private and safe?
Yes. Conversion happens 100% in your browser using JavaScript. Your JSON — including any tokens, IDs, or customer data — never leaves the page and is never sent to a server.
Is the tool free? Do I need an account?
It is completely free with no sign-up, no limits, and no ads cluttering the workspace.
Can it detect dates or enums?
Date strings are kept as `string` (safer than guessing). String values are typed as `string` rather than literal unions, so the output stays stable as your data changes.

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