KToon is a Kotlin Multiplatform serialization library implementing the TOON format (Token-Oriented Object Notation). Think of it as JSON's efficient cousin—perfect for mobile apps, IoT devices, and anywhere bandwidth matters. Build for kiroween hackaton

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JSON (553 bytes):

[
  {"id": 1, "name": "Alice", "email": "alice@example.com", "age": 30},
  {"id": 2, "name": "Bob", "email": "bob@example.com", "age": 25},
  {"id": 3, "name": "Charlie", "email": "charlie@example.com", "age": 35}
]

TOON (179 bytes - 67% smaller!):

users[3]{id,name,email,age}:
  1,Alice,alice@example.com,30
  2,Bob,bob@example.com,25
  3,Charlie,charlie@example.com,35

• 🚀 30-60% smaller payloads - Less data = faster loading
• 📱 True multiplatform - Android, iOS, Desktop, Web (JS + WASM)
• 🔌 Drop-in replacement - Works with your existing @Serializable classes
• ⚡ Fast - Single-pass O(N) serialization
• 🎯 Type-safe - Full kotlinx.serialization integration
• 🛠️ Ktor ready - Client and server ContentNegotiation support
• 🧩 Minimal - ~1000 lines of pure Kotlin, zero platform-specific code

⚠️ TODO: Publish to Maven Central

For now, clone and include as a local module:

git clone https://github.com/JosephSanjaya/ktoon.git

Add to your settings.gradle.kts:

include(:<"path/to/ktoon">)

import io.ktoon.Toon
import kotlinx.serialization.Serializable

@Serializable
data class User(val id: Int, val name: String, val email: String)

fun main() {
    val users = listOf(
        User(1, "Alice", "alice@example.com"),
        User(2, "Bob", "bob@example.com")
    )
    
    // Serialize to TOON
    val toon = Toon.encodeToString(users)
    println(toon)
    // Output:
    // users[2]{id,name,email}:
    //   1,Alice,alice@example.com
    //   2,Bob,bob@example.com
    
    // Deserialize from TOON
    val decoded = Toon.decodeFromString<List<User>>(toon)
    println(decoded) // [User(1, Alice, alice@example.com), User(2, Bob, bob@example.com)]
}

import io.ktor.client.*
import io.ktor.client.engine.cio.*
import io.ktor.client.plugins.contentnegotiation.*
import io.ktor.client.request.*
import io.ktoon.ktor.toon

val client = HttpClient(CIO) {
    install(ContentNegotiation) {
        json()  // Fallback to JSON
        toon()  // Add TOON support
    }
}

// Automatic serialization/deserialization
val users = client.get("https://api.example.com/users") {
    headers {
        append("Accept", "application/toon")
    }
}.body<List<User>>()

import io.ktor.server.application.*
import io.ktor.server.engine.*
import io.ktor.server.netty.*
import io.ktor.server.plugins.contentnegotiation.*
import io.ktor.server.response.*
import io.ktor.server.routing.*
import io.ktoon.ktor.server.toon

fun main() {
    embeddedServer(Netty, port = 8080) {
        install(ContentNegotiation) {
            json()  // For application/json
            toon()  // For application/toon
        }
        
        routing {
            get("/users") {
                val users = listOf(
                    User(1, "Alice", "alice@example.com"),
                    User(2, "Bob", "bob@example.com")
                )
                call.respond(users) // Automatically uses TOON if Accept: application/toon
            }
        }
    }.start(wait = true)
}

This repository includes two demo applications showcasing KToon's versatility:

Real-time format comparison with live backend server.

# Start the backend server
./gradlew :backend:run

# Run the Compose Multiplatform app
./gradlew :composeApp:run

# Or test with curl
curl -H "Accept: application/json" http://localhost:8080/users
curl -H "Accept: application/toon" http://localhost:8080/users

Features:

• Side-by-side JSON vs TOON comparison
• Real-time byte count and savings metrics
• Interactive API testing
• Content negotiation demonstration

Local-first architecture with efficient data storage.

Features:

• Efficient local data storage using TOON
• Batch sync operations
• Configuration file management
• Seed data bundling

• ABOUT.md - Project story and technical deep-dive
• ktoon-core/README.md - Core serialization engine
• ktoon-ktor/README.md - Ktor client integration
• ktoon-ktor/EXAMPLES.md - Usage examples
• ktoon-ktor-server/README.md - Ktor server integration
• backend/README.md - Demo server setup

ktoon/
├── ktoon-core/              # Core serialization engine (~1000 lines)
│   ├── Toon.kt             # Public API
│   ├── ToonEncoder.kt      # Serialization logic
│   ├── ToonDecoder.kt      # Deserialization logic
│   └── ToonLexer.kt        # Tokenization
├── ktoon-ktor/             # Ktor client integration
├── ktoon-ktor-server/      # Ktor server integration
├── backend/                # Demo backend server
└── composeApp/             # Demo Compose Multiplatform app

• Retrofit support - ContentConverter for Retrofit
• OkHttp interceptor

• Maven Central publication
• Comprehensive documentation site
• Binary TOON format
• Compression integration (TOON + gzip)
• Android Studio plugin for visualization

Contributions are welcome! Whether it's:

• 🐛 Bug reports
• 💡 Feature requests
• 📝 Documentation improvements
• 🔧 Code contributions

Please open an issue or PR on GitHub.

Built by Android engineers who noticed the LLM industry was already benefiting from token-efficient formats. We asked: why should only AI companies get these benefits? Mobile apps face the same challenges—limited bandwidth, expensive data plans, slow networks.

KToon brings proven efficiency techniques to the entire Kotlin ecosystem. Whether you're building a social app, e-commerce platform, or IoT controller, you deserve efficient data serialization.

The skeleton is ready. What will you build with it?