What is Kotlin

At a glance

Kotlin is a modern, statically typed programming language created by JetBrains. It targets the JVM, Android, JavaScript, and native platforms through Kotlin Multiplatform. Design goals: conciseness, safety (especially around nulls), smooth interoperability with Java, and excellent tooling in IntelliJ IDEA. Google announced first-class Android support in 2017; today Kotlin is the preferred language for new Android code and is widely used on the server with Spring, Ktor, and beyond.

Created by JetBrains; open source (Apache 2)

Runs on JVM — full Java interop

Also: JS, Native, Multiplatform shared code

Android + server are the largest ecosystems

What makes Kotlin “Kotlin”

Kotlin compiles to the same bytecode as Java on the JVM, so you can call Java libraries from Kotlin and Kotlin from Java without glue code. The standard library adds functional-style operations on collections, scope functions, and coroutines — but the language itself is small and opinionated: immutability with val, nullable types on the type system, and data classes for simple aggregates.

JDK, Kotlin, and the build tool

You still need a JDK on your machine to develop for the JVM — the Kotlin compiler relies on it for the standard Java APIs and for producing JVM bytecode. In practice Gradle or Maven downloads the Kotlin plugin and compiler for you; IntelliJ bundles deep support: navigation, refactoring, and debugging across Java and Kotlin in one project.

Milestones on the timeline

Where Kotlin shows up

✅Kotlin is free and open source under the Apache 2.0 license — no runtime fee, and you can read or fork the compiler on GitHub.