JSON to Kotlin Data Class Converter

Input

Output

Ready

Ln 1, Col 1

Convert JSON to Kotlin in one step

Paste JSON and get Kotlin data classes annotated for kotlinx.serialization, ready for Android, Ktor or any Kotlin project.

How to use it

Paste a JSON sample into the Input panel, open a file, or drop it onto the page. A sample is already loaded so you can see the result.
The Kotlin code appears instantly in the Output panel and updates as you type.
Rename the top-level type under Settings → Root type name, and use Sort keys to order fields alphabetically.
Copy the code or Download it as Root.kt.

What the Kotlin generator produces

@Serializable data class for every object shape.
@SerialName("key") only where the Kotlin name differs from the JSON key.
Optional and nullable values are typed T? with a = null default.
Long, Double, Boolean, List<T>, and JsonElement for mixed values.

Using the generated Kotlin code

Decode with kotlinx.serialization:

val json = Json { ignoreUnknownKeys = true }
val data = json.decodeFromString<Root>(text)
println(data.users.first().name)

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JSON to Kotlin FAQ

Can I use Moshi or Gson instead?

Yes. Replace @Serializable with @JsonClass(generateAdapter = true) and @SerialName with @Json(name = ...) for Moshi, or use @SerializedName for Gson.

Is my data uploaded to a server?

No. The JSON to Kotlin runs entirely in your browser using JavaScript. Your data is never uploaded, logged or stored, and the tool keeps working offline after your first visit.