What Kotlin types are generated?

Strings become String, integers become Long, floats become Double, booleans become Boolean, and null values become Any?. Nested objects become separate data class types with PascalCase names. Arrays become List .

How are serialization annotations added?

Every data class gets @Serializable and each property gets @SerialName("originalKey"). Property names are converted to camelCase. This preserves the original JSON key mapping while following Kotlin naming conventions.

How are optional fields handled?

Fields that are missing from some items in an array are made nullable with the ? suffix and given a default value of null (e.g., val likes: Long? = null). This is compatible with Kotlin's null safety.

DevBento

Tools/JSON to TypeScript & 8+ Languages Generator/Generate Kotlin Data Classes from API Response

Generate Kotlin Data Classes from API Response

Generate Kotlin data classes with kotlinx.serialization annotations from a typical REST API JSON response. Paste your API output and get typed Kotlin code.

Output

Root name

Import path

JSON Input

TypeScript Output

// Generated by DevBento — json-to-typescript
interface RootAddress {
  street: string;
  city: string;
  zip: string;
}

interface RootPostsItem {
  title: string;
  likes?: number;
}

interface Root {
  id: number;
  name: string;
  email: string;
  isActive: boolean;
  roles: string[];
  address: RootAddress;
  posts: RootPostsItem[];
}

Send to:

Paste JSON to pretty-print, minify, validate, or visualize as an interactive graph. Syntax highlighting, tree view, and graph view with export.

ymlJSON / YAML / TOML / CSV / XML / HTML / Markdown

Convert between JSON, YAML, TOML, CSV, XML, HTML, Markdown, and .env in your browser. Paste config or API data and get the equivalent format instantly.

Generate Kotlin Data Classes from API Response

This example generates Kotlin data classes with kotlinx.serialization annotations from a typical REST API response. The pre-filled JSON represents a user object with nested address, array of roles, and array of post objects. Switch to Kotlin mode to see the generated classes.

What You Get

The tool produces:

A root Root data class with @Serializable and @SerialName annotations
RootData class for the nested address object
RootPostsItem class for array items
@SerialName("key") attributes on every property
camelCase property names following Kotlin conventions
Nullable types (T?) with null defaults for optional fields
Kotlin type mappings: String, Long, Double, Boolean, List<String>

How to Use

The example loads with a sample API response and Kotlin mode pre-selected
Inspect the generated Kotlin data classes and their annotations
Copy the classes and paste them into your Kotlin project
Replace with your actual API response to generate classes for your endpoints

Real-World Pattern

Kotlin data classes with kotlinx.serialization are the standard way to deserialize JSON in Android and Kotlin Multiplatform projects. The generated code works directly with Json.decodeFromString<T>(string). Use nullable types with null defaults for fields that may not always be present in the response.

🔒

Nothing you paste leaves this tab. Every tool runs entirely in your browser — no upload, no server, no account.