Kotlin 2025: where the language of the future is heading and why you should be on trend

Kotlin: from "Java killer" to the #1 platform for everything

When JetBrains announced Kotlin in 2011, few believed that this "lightweight" language for the JVM could compete with the giants. A little over a decade later, Kotlin has not just survived — it has burst into the top 10 programming languages according to TIOBE and become the official language for Android. But what's next? In 2025, Kotlin is no longer just a "language for mobile." It is transforming into an ecosystem that covers everything: from servers to browsers and neural networks.

In this article, we will break down the key Kotlin trends, look at real code you can use today, and make a forecast for the next 2-3 years. If you write in Java, Python, or even Swift — take a look at Kotlin. It might be your next step.

Trend #1: Kotlin Multiplatform (KMP) — one code, three platforms

The hottest Kotlin trend in 2024-2025 is Kotlin Multiplatform (KMP). The idea is simple: you write your business logic once in Kotlin, and then compile it for Android, iOS, Web, and Desktop. Sounds like a dream? JetBrains has made it a reality.

Previously, for cross-platform development, you had to sacrifice performance (Flutter, React Native) or put up with limitations (Xamarin). KMP works differently: it compiles to native code for each platform. You don't lose speed, but you save 40-60% of the time writing identical logic.

Example: a shared module for network operations

Let's say you need to write an HTTP client that will work on both Android and iOS. Here's what it looks like in Kotlin using Ktor (an asynchronous library from JetBrains):

// commonMain — common code for all platforms\nimport io.ktor.client.*\nimport io.ktor.client.request.*\nimport io.ktor.client.statement.*\n\nclass ApiClient(private val httpClient: HttpClient) {\n\n    suspend fun fetchUser(id: Int): User {\n        val response: HttpResponse = httpClient.get("https://api.example.com/users/$id")\n        return parseUser(response.bodyAsText())\n    }\n}\n\n// expect/actual — platform-specific code\n// In the Android module:\nactual fun createHttpClient(): HttpClient {\n    return HttpClient(Android) { /* settings for Android */ }\n}\n\n// In the iOS module:\nactual fun createHttpClient(): HttpClient {\n    return HttpClient(Darwin) { /* settings for iOS */ }\n}

Note the keywords expect and actual. They allow you to describe the interface in the common code, and the implementation separately for each platform. This provides flexibility: you are not tied to a single runtime, as in Flutter.

Forecast: By 2026, KMP will become the standard for enterprise applications that require iOS and Android support. JetBrains is already actively promoting it, and Google is testing KMP for its internal projects.

Trend #2: Kotlin for the backend — is Spring Boot fading into the shadows?

Many still associate Kotlin backend only with Android. But on the server side, Kotlin feels just as confident. The Ktor and Spring Boot frameworks with Kotlin wrappers have become mainstream. In 2025, we see a shift: developers are increasingly choosing pure Kotlin (Ktor) instead of "Java in Kotlin syntax" (Spring Boot).

Why? Kotlin offers coroutines — lightweight threads that don't block system resources. In the world of microservices, this provides a huge performance boost.

Example: API on Ktor with coroutines

See how elegant a REST API looks on Ktor:

import io.ktor.server.application.*\nimport io.ktor.server.engine.*\nimport io.ktor.server.netty.*\nimport io.ktor.server.routing.*\nimport io.ktor.server.response.*\n\nfun main() {\n    embeddedServer(Netty, port = 8080) {\n        routing {\n            get("/hello") {\n                call.respondText("Hello, K