Kotlin is a statically typed programming language developed by JetBrains, the company behind the IntelliJ IDEA development environment. JetBrains unveiled it publicly in July 2011. In the announcement post, the team wrote, “JetBrains is unveiling the new project we’ve been working on for almost a year now. The project is Kotlin, a new statically typed programming language for the JVM.”
According to Kotlin’s official FAQ, “The project started in 2010 and was open source from very early on. The first official 1.0 release was in February 2016.” The same FAQ describes the language as one that “targets the JVM, Android, JavaScript, Wasm, and Native,” and notes that “when targeting the JVM, Kotlin produces Java-compatible bytecode.” Because Kotlin compiles to ordinary JVM bytecode and interoperates with Java, existing Java code and Kotlin code can be mixed in the same project.
A central design goal was safety. The FAQ explains that Kotlin “is also more type-safe — for example, support for non-nullable types makes applications less prone to NPE’s.” By distinguishing nullable from non-nullable types in the type system, Kotlin moves a large class of null-reference errors from run time to compile time. Combined with more concise syntax than Java, this made it attractive for large application codebases.
Kotlin’s most consequential adoption came on Android. The official FAQ states plainly, “Kotlin is supported as a first-class language on Android,” and lists production applications such as Basecamp and Pinterest that use it. That first-class status, announced by Google in 2017, helped Kotlin move from a JetBrains project into one of the most widely used languages for mobile development.