Does it handle nested objects?

Yes. Every nested object becomes its own data class named after the property, referenced from the parent.

How are numbers typed?

Whole numbers map to Int and decimals map to Double. Change them manually if you need Long or BigDecimal.

What about null values?

A null in the sample JSON produces Any? — replace it with the real type once you know it. Nullables can default to null.

Do I need kotlinx.serialization?

No. Toggle it off to get plain data classes without annotations or imports.

Is my data uploaded to a server?

No. This tool runs entirely in your browser using standard web APIs, so your input never leaves your device and nothing is logged or stored on our servers.

JSON to Kotlin Data Class

Generate Kotlin data classes from any JSON payload.

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Root class name

kotlinx.serialization

Default nullables to null

JSON input

Kotlin data classes

import kotlinx.serialization.SerialName
import kotlinx.serialization.Serializable

@Serializable
data class Root(
    val id: Int,
    val name: String,
    val active: Boolean,
    val score: Double,
    val tags: List<String>,
    val address: Address,
    val nickname: Any? = null
)

@Serializable
data class Address(
    val city: String,
    val zip: String
)

About the JSON to Kotlin Data Class

Paste a JSON object or array and get idiomatic Kotlin data classes, including nested classes for embedded objects, List<T> for arrays, nullable types for nulls, optional kotlinx.serialization annotations with @SerialName for non-camelCase keys, and default null values.

Examples

Simple object

{"id":1,"name":"Ada"}

Output

data class Root(
    val id: Int,
    val name: String
)

Keyboard shortcuts

Copy the main outputCtrl / ⌘ + Shift + C
Download the resultCtrl / ⌘ + S
Share this toolCtrl / ⌘ + Shift + S
Reset the inputsAlt + R
Open the tool search paletteCtrl / ⌘ + K

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Frequently asked questions

Version 1.0.0 · Updated 2026-08-19 · Runs entirely in your browser