Kotlin runtime jar vs kotlin stdlib jar

Question

What's the difference between kotlin-runtime.jar (225.1K) and kotlin-stdlib.jar (727.3K) (sizes are for 1.0.0-beta-1103 version)? Which one should I distribute with my application? For now I live with kotlin-stdlib.jar, because that's what Android Studio generated, but I wonder if I can use kotlin-runtime.jar since it's smaller.

Answer 1

The runtime library only contains base Kotlin language types required to execute compiled code. It is a minimal classes set required.

The standard library contains utility functions you need for comfortable development. These are such functions for collections manipulations, files, streams and so on.

In theory you can use just runtime but you generally shouldn't because there are no standard library in it so you will lose many utility functions required for comfortable development (such as map, filter, toList and so on) so I don't think you should.

So in fact you need both. If you need make the result package smaller then you can process you app with proguard.

Update

Starting from Kotlin 1.2, kotlin-runtime and kotlin-stdlib are merged into single artifact kotlin-stdlib.

We merge kotlin-runtime and kotlin-stdlib into the single artifact kotlin-stdlib. Also we’re going to rename kotlin-runtime.jar, shipped in the compiler distribution, to kotlin-stdlib.jar, to reduce the amount of confusion caused by having differently named standard library in different build systems. That rename will happen in two stages: in 1.1 there will be both kotlin-runtime.jar and kotlin-stdlib.jar with the same content in the compiler distribution, and in 1.2 the former will be removed.

Refer to Kotlin 1.1: What’s coming in the standard library for details.