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JSON to TypeScript

Generate TypeScript interfaces from a sample JSON payload.

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Quick Tool Overview

The JSON to TypeScript converter generates interfaces from a sample payload: a named interface per nested object, element types for arrays, optional markers for keys that are not always present, and unions with null where nulls appear.

What it does
Generates TypeScript interfaces from a JSON sample
You give it
An API response or any JSON document
You get back
Typed interfaces or type aliases, ready to paste
Best for
Typing an API client without writing the models by hand
Developer Tools Free, unlimited use No sign-up Runs in your browser

About the JSON to TypeScript

Paste an API response and get the interfaces for it. Every nested object becomes its own named interface, arrays are typed by their element, and a field missing from some elements of an array is marked optional with a question mark.

The inference merges rather than guessing from the first item. An array whose objects differ slightly produces one interface covering all of them, with the sometimes-present keys optional and a widened type where an integer and a decimal both appear. Nulls become a union with null rather than being silently dropped. You can emit interfaces or type aliases, name the root type, and make every field optional in one click for the partial-update shapes a PATCH endpoint takes.

Key features of the JSON to TypeScript

Types are merged, not guessed

An array of slightly different objects produces one interface covering all of them, rather than a type built from the first item alone.

Optional fields are marked

A key missing from some records gets a question mark, so your compiler forces you to handle its absence.

Nulls become unions

A field that is sometimes null is typed string | null rather than any, which keeps strict null checking useful.

Interface or type alias

Emit whichever your codebase uses; interfaces are extensible, type aliases compose more freely.

All-optional mode

Make every field optional in one click for the partial shapes a PATCH endpoint accepts.

How to use the JSON to TypeScript

  1. 1

    Paste a JSON sample

    A real API response gives the best result; an array of records is ideal.

  2. 2

    Name the root type

    Set the name for the top-level interface — the nested ones are named from their keys.

  3. 3

    Choose interface or type

    Interfaces are extensible; type aliases compose more freely. Pick what your codebase uses.

  4. 4

    Copy into your project

    Paste the result into a .ts file, or download it directly.

Frequently asked questions

When the sample is an array of objects and a key is missing from at least one of them. From a single object it cannot tell, so pass a representative array whenever you can.

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