Kotlin is another programming language for Android, which is essentially just a streamlined version of Java. It is also a free, open-source tool. Compiling an application written in Kotlin will still combine the same artifacts into the .apk application package (classes.dex, resource files, and the AndroidManifest.xml among others).

When examining unobfuscated code, slight differences in syntax language exist that can be seen when analyzing the classes.dex files. The major difference between Kotlin-developed applications and Java is that applications developed in Kotlin will have a slightly larger size, which can be directly attributed to the existence of an extra “kotlin” directory and a larger classes.dex file. Other main items, like the AndroidManifest.xml, resources.arsc and res, will have the exact same size as their Java-based counterparts.¹ Compiling obfuscated code will result in identically sized classes.dex files when performing static code analysis. This is likely due to how the obfuscation is handled within Android Studio prior to compiling.

Reference:

[1] https://for585.com/kotlin