Home/JSON → TypeScript
JSON · TS

JSON → TypeScript

Generate TypeScript interface / type declarations from JSON

Style
Input JSONJSON
Lines: 0Chars: 0
Output TypeScriptTS
Lines: 0Chars: 0

Overview: The JSON → TypeScript type generator inspects a sample JSON payload and automatically infers TypeScript interface or type declarations. It saves front-end engineers from hand-writing repetitive type definitions when integrating with back-end APIs. Nested objects are split into independent types, array elements are merged, and identical anonymous object shapes are deduplicated and reused.

How to use: Step 1 — paste a realistic JSON response into the left panel or click "Sample" to load an example. Step 2 — enter the root type name (default: RootObject). Step 3 — choose the output style: interface is better for extensible object declarations, while type is more flexible and composes well with unions. Step 4 — the right panel produces complete type code in real time; copy it into your project or download it as types.ts. Every generated type has the export keyword so it is ready to consume directly.

Typical scenarios: Generate TS types from Swagger or Postman example responses during front-end / back-end integration; grab sample data from third-party API docs and quickly build a type library; add types to Firebase or Supabase BaaS payloads; build Options interfaces from configuration samples when developing utility libraries; batch-import types when migrating a legacy JavaScript project to TypeScript.

Technical notes: Primitives are inferred as string, number, boolean or null. Empty arrays become any[], mixed-type arrays produce a union. Field names that are not valid JS identifiers are quoted. Nested object type names are PascalCased from the parent key. Objects with identical shapes only produce a single declaration. Generated types do not include the optional modifier (?); tweak by hand if you need optional fields.

Privacy: Type inference is performed entirely in your browser. The JSON you provide is never uploaded, so you can use it safely with production API responses.

Frequently Asked Questions

How do I use JSON → TypeScript?
Step 2 — enter the root type name (default: RootObject ). Step 3 — choose the output style: interface is better for extensible object declarations, while type is more flexible and composes well with unions.
What can JSON → TypeScript do?
Typical scenarios: Generate TS types from Swagger or Postman example responses during front-end / back-end integration; grab sample data from third-party API docs and quickly build a type library; add types to Firebase or Supabase BaaS…
Is my data private when I use JSON → TypeScript?
The JSON you provide is never uploaded, so you can use it safely with production API responses. The JSON you provide is never uploaded, so you can use it safely with production API responses.
What technical details should I know about JSON → TypeScript?
Field names that are not valid JS identifiers are quoted. Objects with identical shapes only produce a single declaration.