Mock JSON · Gson · Moshi · kotlinx — 3 modes
Convert Kotlin to JSON
Mock data, snippets
or framework guide.
Generate mock JSON from a Kotlin data class, get Gson, Moshi and kotlinx.serialization snippets, or get Retrofit and Ktor JSON patterns. Three modes, one tool.
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data class → mock JSON
Gson · Moshi · kotlinx snippets
Retrofit · Ktor patterns
Always free
Kotlin to JSON — 3 modes
100% client-side
Kotlin data class input
Ready
Gson vs Moshi vs kotlinx.serialization
The three Kotlin JSON libraries and their one-liner serialization.
| Library | Serialize | Best for |
|---|---|---|
| Gson | Gson().toJson(obj) |
Legacy Android projects · zero annotations needed · Retrofit GsonConverterFactory |
| Moshi | moshi.adapter(T::class.java).toJson(obj) |
Modern Android · Kotlin-first · null-safe · Retrofit MoshiConverterFactory |
| kotlinx | Json.encodeToString(obj) |
KMP · Ktor · official Kotlin library · all targets (Android, iOS, Web, Desktop) |
Kotlin parsed in your
browser. No IDE needed.
The mock JSON parser reads Kotlin data class property declarations — val/var with type annotations. It handles nullable types (Type?), List<T> generics and nested class references. The snippets cover the three main Kotlin JSON libraries with complete Gradle dependency coordinates and all common serialization scenarios.
3 libraries covered
Gson, Moshi and kotlinx.serialization — complete Gradle dependencies, imports and real-world usage patterns for each.
Retrofit + Ktor patterns
Complete Retrofit service interface with @Body annotation and Ktor client with ContentNegotiation plugin — the two main HTTP clients for Kotlin.
KMP-ready
The kotlinx.serialization and Ktor patterns work on all Kotlin Multiplatform targets — Android, iOS, Desktop and Web.
52 tools, always free
No watermarks, no account. Funded by non-intrusive display advertising only.
Frequently asked questions
How do I convert a Kotlin data class to JSON?
With Gson: val json = Gson().toJson(myObject). With kotlinx.serialization: annotate with @Serializable then call Json.encodeToString(myObject). With Moshi: build a Moshi instance and get a JsonAdapter. Select the Snippets mode for complete code with Gradle dependencies.
Which Kotlin JSON library should I use?
For new Android projects: Moshi with codegen adapters — Kotlin-first, null-safe, no reflection. For Kotlin Multiplatform: kotlinx.serialization — the only option that works on all targets. For legacy Android: Gson — zero configuration, works without annotations. All three integrate with Retrofit.
Is the Kotlin to JSON converter free?
Yes, completely free. No account required. JSONSwitcher is funded by non-intrusive display advertising.