Kotlin (Programming Language)

Kotlin is a general-purpose programming language created by JetBrains, the company behind the IntelliJ family of developer tools, and released as open source under the Apache 2.0 license. It is statically typed, meaning the types of values are checked before the program runs, which catches a class of bugs early, and it uses type inference so developers rarely have to spell those types out. Its headline trait is conciseness — Kotlin does the same work as older languages with far less boilerplate code — combined with features aimed at safety, most notably null safety in the type system, which is designed to prevent the null-reference errors that plague many codebases. Kotlin mainly targets the Java Virtual Machine but can also compile to JavaScript or, through LLVM, to native code.

The defining fact for most teams is that Kotlin is fully interoperable with Java. Kotlin code can call Java code and vice versa, in the same project, so a team can adopt Kotlin gradually inside an existing Java application rather than rewriting everything. That interoperability is why Kotlin spread so quickly: it slots into the enormous installed base of Java software and the Android runtime without forcing a clean break. It is worth stating plainly what Kotlin is not — it is not a marketing platform, an analytics tool, or anything martech-specific. It appears in a marketing glossary only because teams building mobile apps and backend services encounter it, and knowing what it is prevents confusion.

Kotlin's most prominent role is in Android development. In 2017 Google announced official support for Kotlin on Android, and in 2019 it went further, naming Kotlin its preferred language for Android app development. Since then Kotlin has become the default choice for new Android apps, used by a large majority of professional Android developers, with Java still supported for legacy code. The appeal on Android is the same as elsewhere — less boilerplate, safer handling of nulls, and modern language features — plus first-class tooling and libraries that Google now builds Kotlin-first. For a product team, this means an Android app written in Kotlin is on the mainstream, well-supported path, which matters for hiring, maintenance, and access to new platform capabilities.

Kotlin's reach extends past Android through Kotlin Multiplatform, which lets teams share code across Android, iOS, web, and backend targets while still writing platform-specific code where needed. That can reduce duplicated logic between an Android and an iOS app, for instance. Still, the language's center of gravity is the JVM and Android, and that is where most marketing-adjacent teams will meet it — in the mobile app that serves customers, sends push notifications, or captures analytics events. Understanding that Kotlin is the language the app is written in, not a marketing capability itself, keeps the mental model straight when a developer mentions it in a planning conversation.

A marketing or product team does not write Kotlin, but it benefits from knowing when the word appears. If your company ships an Android app, it is very likely built in Kotlin, and that choice affects how quickly new features — a redesigned onboarding flow, a promotion screen, an in-app message — can be built and maintained. Kotlin's conciseness and safety tend to mean faster iteration and fewer crashes, and crashes matter commercially: an app that crashes less keeps more users through the funnel. So when engineering says the app is in Kotlin, read it as being on a modern, well-supported track rather than as a red flag or a cost.

The confusions to avoid are simple. Do not mistake Kotlin for a marketing, analytics, or automation tool — it is a general-purpose language, and nothing about it is martech-specific. Do not assume choosing Kotlin locks you out of Java, since the two interoperate freely in the same codebase. And do not treat the language choice as the thing that determines app quality on its own — Kotlin makes good engineering easier, but the outcome still depends on the team and the product decisions. Knowing what Kotlin is, and what it is not, is enough for a marketer to have a grounded conversation with the engineers who use it.

Kotlin, named after an island near St. Petersburg, was created by JetBrains and first released in 2016, gaining official and then preferred status for Android.

Etymology: source.

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