data class or regular class?

`data class` by default — gives you equals/hashCode/toString/copy for free and matches Kotlin idioms. Regular class option available for advanced use.

How are nullable fields detected?

Fields that don't appear in every sample record become `Type?` (nullable). Always-present fields are non-nullable. Error-prone with small samples — review the output.

What serialization libraries are supported?

kotlinx.serialization, Jackson, Gson, and Moshi. Pick based on your project; each has slightly different annotation style.

Does it support sealed class hierarchies?

Not auto-detected. If your JSON has a discriminator (e.g. `type: "foo"`), manually create the sealed hierarchy — the tool generates the leaves.

JSON → Kotlin Class | DevTools Surf

DevTools Surf

Example: JSON → Kotlin Class

A worked example, rendered from real sample data. Sign in to run the tool on your own input.

Input

{"id":1,"name":"Kotlin","stable":true,"versions":[1.8,1.9,2.0]}

Output

data class Root(
    val id: Int,
    val name: String,
    val stable: Boolean,
    val versions: List<Double>
)

About JSON → Kotlin Class

JSON → Kotlin Class preview - Converters tool

Generate a Kotlin data class from a JSON sample. Part of the DevTools Surf developer suite. Browse more tools in the Converters collection.

Use Cases

Android developers deserializing API responses with Gson or Moshi
Backend engineers building Ktor or Spring Boot services
Data engineers creating type-safe models for JSON event streams
Mobile teams replacing verbose Java POJOs with concise data classes

Tips

Nested JSON objects produce nested data classes with proper typing
Mark nullable fields with Kotlin's ? syntax for safe API parsing
Copy the generated class directly into your Android Studio project

Fun Facts

Kotlin data classes automatically generate equals(), hashCode(), toString(), and copy() methods — saving roughly 80 lines of Java boilerplate per class.
Kotlin was named after Kotlin Island near St. Petersburg, Russia, following the tradition of Java being named after the Indonesian island.
Google announced Kotlin as a first-class Android language at Google I/O 2017, and by 2020 over 70% of the top 1,000 Android apps used it.

FAQ

data class or regular class?: `data class` by default — gives you equals/hashCode/toString/copy for free and matches Kotlin idioms. Regular class option available for advanced use.
How are nullable fields detected?: Fields that don't appear in every sample record become `Type?` (nullable). Always-present fields are non-nullable. Error-prone with small samples — review the output.
What serialization libraries are supported?: kotlinx.serialization, Jackson, Gson, and Moshi. Pick based on your project; each has slightly different annotation style.
Does it support sealed class hierarchies?: Not auto-detected. If your JSON has a discriminator (e.g. `type: "foo"`), manually create the sealed hierarchy — the tool generates the leaves.

Related Converters Tools

JSON to XML JSON to CSV JSON to YAML JSON to TSV JSON to String XML to JSON XML to CSV XML to String