The fastest JSON path for Kotlin Multiplatform: up to 2.7× faster than other serializers, with up to 86% less memory, and proven against the industry's conformance suite.

• Built for speed. Compile-time generated serializers, SWAR parsing and zero-allocation hot paths: 1.07 GB/s decoding bytes and 1.2 GB/s decoding strings on a real 631 KB payload, and faster than the alternatives on every channel we measure.
• Proven, not promised. All 318 cases of JSONTestSuite, the industry-standard JSON parser conformance suite, pass on the string, bytes and streaming channels. Coverage-guided fuzzing has executed more than 765 million cases against the readers and writers with 0 crashes.
• Resilient by design. When the backend ships messy JSON, Ghost can keep parsing where you opt in, and tells you exactly where it went wrong.

Keep the stack you have: kotlinx.serialization, Moshi, Gson or Jackson, with Ktor, Retrofit or Spring. Add one annotation to the DTOs that carry your traffic and Ghost takes over exactly that path. It is not a rewrite. It is an upgrade where it counts.

Quick Start: first DTO in minutes → · Try it in the browser → · Maven Central · Roadmap

Up to 2.7× faster and 86% leaner than kotlinx.serialization and Moshi on every channel we measure, and the gain grows with payload size. Adopt it one DTO at a time or across your whole model layer.

Twitter macro (631 KB) decode:

Benchmarks · HTTP Arena · Playground Speed Test

Add @GhostSerialization to a model. Keep @Serializable if you already use KotlinX: its call sites keep working.

@Serializable                 // keep: KotlinX call sites still work
@GhostSerialization           // add: Ghost codegen for this class only
data class User(
    @SerialName("user_id")    // keep: Ghost uses this as the wire name
    val id: Long,
    val name: String,
)

Ghost.deserialize<User>(responseBytes)

Drop-in for Ktor, Retrofit and Spring, with the same stack you have today. It also keeps parsing when the backend ships messy JSON (@GhostResilient, @GhostFallback, RawJson) and its errors include the JSONPath of the failure.

Also: Android · iOS · JVM · Wasm (iOS/Wasm with no registration code, via the Gradle plugin) · YAML · Proto3 JSON · Kotlin 2.2.21+ / KSP 2.3.x / Ktor 3.3.x+ → Modules

• JSON conformance: all 318 cases of JSONTestSuite behave correctly on the string, bytes and streaming channels, in lenient and in strict mode.
• Fuzzing: more than 765 million coverage-guided executions (Jazzer) across the readers and writers, 0 crashes.
• Differential testing: the channels are checked against each other and against kotlinx.serialization on every build, and every night with a fresh seed; 8,934 real-world JSON files decode to the same tree as kotlinx.serialization.
• YAML: 96.06% of yaml-test-suite decodes exactly right (268/279) and the writer round-trips 100%.

Details and how to run each check → Quality and conformance

Quick Start · Installation · Android · KMP / Ktor · iOS · Spring · YAML · Proto3 JSON · Advanced · Quality · Architecture · Contributing · Support & Versioning

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