Plug Serialization into Ktor
Install ContentNegotiation for automatic decoding.
Plug Serialization into Ktor is a free Kotlin Multiplatform Academy lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Kotlin Multiplatform Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Stop Parsing by Hand
You could decode every response manually, but Ktor can wire serialization in so requests and replies become typed automatically.
Meet ContentNegotiation
The ContentNegotiation plugin teaches the HttpClient how to convert request and response bodies to and from your models.
Add the Dependency
First add the Ktor content-negotiation artifact plus the JSON serializer module to commonMain.
implementation("io.ktor:ktor-client-content-negotiation:2.3.12")Add the JSON Bridge
You also include the ktor-serialization-kotlinx-json module, which connects Ktor to kotlinx.serialization specifically.
implementation("io.ktor:ktor-serialization-kotlinx-json:2.3.12")Install on the Client
Inside the HttpClient builder you install ContentNegotiation and register the json converter once.
install(ContentNegotiation) { json() }Configure the Json
The json block accepts a configured Json instance, so you can pass ignoreUnknownKeys and friends right here.
json(Json { ignoreUnknownKeys = true })Decode Automatically
Now a GET can return your model directly. Ktor reads the body and hands you a typed object with no manual decode call.
val user: User = client.get(url).body()Encode Request Bodies
The same plugin serializes outgoing data, so you can setBody with a Kotlin object and Ktor writes the JSON for you.
post(url) { setBody(user) }Set the Content Type
When sending a body, declare contentType as application/json so the server reads it correctly.
contentType(ContentType.Application.Json)One Setup, Both Apps
Because all of this lives in commonMain, Android and iOS share the identical typed networking with zero duplicate code.
Clean End to End
Ktor plus serialization gives you a tidy pipeline: call an endpoint, get a model, send a model, all type-safe across platforms.
Quick Check
Which Ktor plugin enables automatic JSON decoding of responses?
Recap
Install ContentNegotiation with json() on your HttpClient so Ktor auto-encodes request bodies and decodes responses into typed models on both apps.
Frequently asked questions
Is the “Plug Serialization into Ktor” lesson free?
Yes — the full text of “Plug Serialization into Ktor” is free to read here on the web, and the Kotlin Multiplatform Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Kotlin Multiplatform Academy course, upgrade to CoddyKit PRO.
What will I learn in “Plug Serialization into Ktor”?
Install ContentNegotiation for automatic decoding. You practise Kotlin Multiplatform Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Kotlin Multiplatform Academy?
No prior experience is required. Kotlin Multiplatform Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Plug Serialization into Ktor” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Kotlin Multiplatform Academy lesson?
Yes. Every Kotlin Multiplatform Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- @Serializable Data Models
- @SerialName & Custom Field Mapping
- Nullable, Default & Optional Fields
- Plug Serialization into Ktor