Kotlin is a programming language that is an alternative to Java. Kotlin is a popular option for people who develop applications and software for the Android mobile operating system. Your duties as a Kotlin developer include writing code for applications, testing your designs, and debugging the code. Some programmers who use Kotlin also use Java, Objective-C, and Swift to create apps and programs for different operating systems and platforms. Software engineers plan and oversee the entire development cycle for Kotlin programming projects using methodologies like Scrum and Agile. You can either develop apps for a company or independently.