Ktor Framework Cheatsheet

Ktor is a modern, asynchronous web framework for building backend applications in Kotlin. It is designed to be concise, expressive, and easy to use. Whether you’re a seasoned developer or just getting started with Ktor, having a cheatsheet can be incredibly handy. In this blog post, we’ll provide a quick reference guide code snippets to help you navigate the essentials of the Ktor framework.

Getting Started


To get started with Ktor, you need to add the necessary dependencies to your project. This can be done using a build tool like Gradle or Maven. Here’s an example for Gradle:

// build.gradle.kts

plugins {
    kotlin("jvm") version "1.5.20"

application {
    mainClassName = "com.example.ApplicationKt"

dependencies {
    implementation "io.ktor:ktor-server-netty:1.6.4"
    implementation "io.ktor:ktor-html-builder:1.6.4"
    implementation "io.ktor:ktor-features:1.6.4"
    implementation "io.ktor:ktor-gson:1.6.4"

Application Setup

Now, let’s set up a basic Ktor application. Create a Kotlin file (e.g., Application.kt) with the following code:

// Application.kt

import io.ktor.application.*
import io.ktor.features.ContentNegotiation
import io.ktor.features.StatusPages
import io.ktor.http.ContentType
import io.ktor.http.HttpStatusCode
import io.ktor.jackson.jackson
import io.ktor.request.receive
import io.ktor.response.respond
import io.ktor.routing.*
import io.ktor.server.engine.embeddedServer
import io.ktor.server.netty.Netty

fun main() {
    embeddedServer(Netty, port = 8080) {
        install(ContentNegotiation) {
            jackson {
                // Configure Jackson here if needed

        install(StatusPages) {
            exception<Throwable> { cause ->
                call.respond(HttpStatusCode.InternalServerError, cause.localizedMessage)

        routing {
            // Define your routes here
    }.start(wait = true)


Basic Routing

Ktor provides a simple and expressive way to define routes. Here’s an example:

routing {
    route("/api") {
        get("/hello") {
            call.respondText("Hello, Ktor!")

Path Parameters

You can easily extract path parameters from the URL:

routing {
    get("/user/{id}") {
        val userId = call.parameters["id"]
        call.respondText("User ID: $userId")

Handling Requests and Responses

Request Body

To handle incoming JSON requests, use the receive function:

data class User(val name: String, val age: Int)

routing {
    post("/user") {
        val user = call.receive<User>()
        call.respondText("Received user: $user")

Responding with JSON

Use the respond function to send JSON responses:

routing {
    get("/user") {
        val user = User("John Doe", 25)

This cheatsheet provides a quick reference guide for some fundamental aspects of the Ktor framework. As you explore Ktor further, you’ll discover more features and capabilities that make it a powerful choice for building modern, asynchronous web applications in Kotlin.


1. What is Ktor, and why should I use it?

Ktor is a modern, asynchronous web framework for building backend applications in Kotlin. It offers a concise and expressive syntax, making it easy to develop robust web applications. If you’re already familiar with Kotlin, Ktor provides a seamless and enjoyable experience for building web services.

2. How do I handle errors in a Ktor application?

Ktor allows you to handle errors using the StatusPages feature. By installing this feature, you can define how your application responds to different types of exceptions, providing a centralized way to manage errors and present appropriate responses to clients.

3. Can Ktor handle JSON requests and responses?

Yes, Ktor has built-in support for handling JSON. You can use the ContentNegotiation feature and include a JSON serialization library like Jackson to handle incoming JSON requests and respond with JSON data easily. This simplifies the development of RESTful APIs.

4. How do I set up routing for my Ktor application?

Routing in Ktor is straightforward. You can define routes using the routing block and specify HTTP methods along with path patterns. For instance, you can use the get, post, and route functions to define the behavior for different endpoints in your application.

5. Is Ktor suitable for microservices?

Yes, Ktor is well-suited for building microservices. Its lightweight nature, asynchronous design, and ease of use make it a good fit for developing scalable and performant microservices. Additionally, Ktor’s extensibility allows you to tailor your microservices architecture to specific project requirements.