You can check a side by side comparison of Swift and Kotlin here. It provides the most important Swift features (optionals, extensions, generics, lambdas.) and a very similar syntax. If you are a Swift developer, you will love Kotlin. It adds lots of great features while at the same time it keeps complete interop with Java, which means that you can combine them both together as you prefer. Kotlin is a great language, it is to Android/Java what Swift is to iOS/Objective-C. It comes with a desktop Mac application to copy & paste your code, as well as a command line tool to transform a complete project to Kotlin. It does string transformations as well as some more complicated ones like transforming guard statements to negative if statements, properties, memory management and many others.

It applies transformations to the Swift code to get as correct as possible Kotlin code (see limitations below). SwiftKotlin is a framework, a command line tool and a Mac application for translating Swift code into Kotlin. A tool to convert Swift code to Kotlin in a very easy and quick way.

Swift to kotlin converter