JSON to Kotlin converter

Generate Kotlin from JSON locally

Kotlin services and Android apps prefer data classes over Java-style POJOs. Turning a JSON sample into data class declarations with nullable types and List properties gives you idiomatic models ready to paste into a module.

What the Kotlin output includes

• Objects become data class declarations with val properties
• Optional JSON keys become nullable properties with = null defaults
• JSON arrays map to List<T>; null samples produce T?
• A root JSON array becomes a typealias to List of the item data class

How to convert JSON to Kotlin

1. Paste JSON or drop a .json file into the converter.
2. Choose a Root name for the top-level type if needed, then convert.
3. Copy or download the Kotlin output — processing stays local.

FAQ

Is this JSON to Kotlin converter free?

Yes. Formatly generates Kotlin data classes from JSON in the browser at no cost and without an account.

Is my JSON uploaded?

No. The converter runs on this device. Your payload is not sent to Formatly servers.

How are missing fields handled?

When the same object shape appears with different keys in an array, missing keys become nullable properties defaulting to null.