Kotlin and Android applications: diffusion and adoption of characteristic constructs Context: In October 2017, Google introduced Kotlin as a first class programming language for android applications. Kotlin is an Object oriented programming compatible with java, with the addition of some practices that helps to reduce number of code lines, exceptions and many other issues. Many mobile applications started a transition by changing the base code from java to Kotlin. Goal: The main objective of the article is to study the impact of Kotlin on open source android applications on GitHub. To analyze the impact the paper were divided into three parts.