Speed up your high-traffic paths by 66% using 50% less memory — without touching your legacy APIs.

Ghost is a byte-first, compile-time JSON serializer designed for Kotlin Multiplatform (Android, iOS, and JVM) that acts as a drop-in optimization. It coexists seamlessly with your existing setup (like kotlinx.serialization, Jackson, or Gson), allowing you to adopt it incrementally in native mobile apps and high-traffic backends (Ktor, Retrofit, Spring Boot).

👉 Try the Interactive Demo →   |   📦 Maven Central → · 1.2.7

Ghost generates all serialization code at compile time via KSP — and then goes several steps further:

Result on HTTP Arena Kotlin frameworks (3-framework comparison, composite score). Ghost replaces Ktor's default JSON codec with compile-time serializers and zero-copy parsing — higher throughput on real API workloads with lower memory pressure.

Source: http-arena.com — Kotlin filter, ktor-ghost vs ktor vs fishcake. Wire Ghost via install(ContentNegotiation) { ghost() } and bodyGhost<T>() / respondGhost() to bypass generic negotiation on hot paths.

▶️ Watch the Demo Video (docs/ghost.mp4) →

Real benchmark on Android vs KotlinX Serialization — running in the ghost-sample Compose Multiplatform app.

• 📊 HTTP Arena Benchmarks → — ktor-ghost composite 831 vs plain ktor 728 (+14%); see table above for per-workload RPS.
• 📈 benchmarks.md — Full multi-engine tables (Ghost, KSER, Gson, Jackson), stress tests, special-feature benchmarks, run instructions.

# gradle/libs.versions.toml
[versions]
ghost = "1.2.7"
ksp   = "2.1.10-1.0.31"

[libraries]
ghost-api           = { module = "com.ghostserializer:ghost-api", version.ref = "ghost" }
ghost-serialization = { module = "com.ghostserializer:ghost-serialization", version.ref = "ghost" }
ghost-compiler      = { module = "com.ghostserializer:ghost-compiler", version.ref = "ghost" }

// build.gradle.kts
plugins {
    id("com.google.devtools.ksp") version "2.1.10-1.0.31"
    id("com.ghostserializer.ghost") version "1.2.7"
}

@GhostSerialization
data class User(val id: Long, val name: String, val email: String)

val user: User = Ghost.deserialize(responseBytes)  // ByteArray — fastest path
val json: String = Ghost.encodeToString(user)

You don't need to rewrite your entire project. Ghost can coexist seamlessly with your existing setup (like kotlinx.serialization, Jackson, or Gson).

If a class does not have the @GhostSerialization annotation, request/response negotiation automatically falls back to your standard serializer. This means you can adopt Ghost incrementally, using it only on your highest-traffic endpoints!

import io.ktor.serialization.kotlinx.json.*
import io.ktor.server.application.*
import io.ktor.server.plugins.contentnegotiation.*
import com.ghost.serialization.ktor.ghost
import kotlinx.serialization.json.Json

fun Application.module() {
    install(ContentNegotiation) {
        // 1. Kotlinx.serialization (or Jackson/Gson) handles the standard endpoints
        json(Json { ignoreUnknownKeys = true })
        // 2. Ghost handles high-performance @GhostSerialization endpoints as fallback
        ghost() 
    }
}

import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory
import com.ghost.serialization.retrofit.GhostConverterFactory

val retrofit = Retrofit.Builder()
    .baseUrl("https://api.example.com")
    // 1. GhostConverterFactory handles @GhostSerialization endpoints
    .addConverterFactory(GhostConverterFactory.create()) 
    // 2. GsonConverterFactory (or Moshi / Kotlinx.serialization) handles the rest as fallback
    .addConverterFactory(GsonConverterFactory.create())
    .build()

With the ghost-spring-boot-starter dependency added, coexistence is fully automatic. The starter automatically registers GhostHttpMessageConverter (for Spring MVC) and GhostReactiveEncoder/GhostReactiveDecoder (for Spring WebFlux) at the beginning of the message converter/codec chain:

• Request and response bodies using classes annotated with @GhostSerialization are processed by Ghost for maximum performance.
• Any other types automatically fall through and are processed by your standard serializer (like Jackson).

No manual configuration is required!

→ Full modules guide →

Guide	Platform / Category	Description
Modules & Integrations		All artifacts, framework integrations, and platform targets
Installation		Version catalog, KSP setup, ghost.textChannel opt-in
Usage — Android		Gradle plugin, Retrofit, Resilience, Custom Decoders
Usage — KMP		Shared module, Ktor, Sealed classes, Structural Transformations
Usage — iOS / Swift		XCFramework export, Bridge setup, Alamofire integration
Usage — Spring Boot		Auto-config, MVC + WebFlux, @GhostStrict, @GhostCoerce
Usage — Protobuf		@GhostProtoSerialization, proto3 JSON mapping, Well-Known Types, known limitations
Advanced Features		Byte-first, @GhostFlatten, @GhostWrap, Contextual Serializers, Platform limits
Type System		Supported field types, opaque JSON, collections, unsupported patterns
Architecture		Compiler pipeline, buffer pool mechanics, O(1) bitwise field matching
Benchmarks		Full results, run instructions, JIT log analysis
Contributing		Dev environment, test modules, PR checklist, supported platforms

Ghost uses three reader types and two writer types, all generated by KSP:

Ghost.deserialize<User>(bytes: ByteArray)
  └─ GhostJsonFlatReader          ← zero alloc, bitwise trie field match
Ghost.deserialize<User>(json: String)
  └─ GhostJsonStringReader        ← native char[] scan, no encodeToByteArray
Ghost.deserializeStreaming<User>(source: BufferedSource)
  └─ GhostJsonReader              ← O(1) memory regardless of payload size

Ghost.encodeToBytes(user)         → GhostJsonFlatWriter (pre-encoded headers, thread-local pool)
Ghost.encodeToString(user)        → FlatCharArrayWriter (pooled, platform-tuned warm capacity)

All paths are fully monomorphic — the JIT compiles them to near-native throughput after warmup.

For a deep dive into the compiler plugin, thread-local buffer pool mechanics, and fast parsing architecture, see the Architecture Guide →.

git clone https://github.com/juanchurtado1991/ghost-serializer.git
./gradlew ciTestJvm          # JVM modules (Linux / macOS / Windows)
./gradlew ciTest             # + Android unit tests; + iOS on macOS

→ Full contributing guide → — dev environment, adding test modules, benchmarks, PR checklist.

See CHANGELOG.md for version history.

Apache 2.0

Developed with ❤️ by the Ghost Serializer team. 👻