The kotlinx.serialization library supports serialization of Kotlin classes to different formats on all supported platforms. If you ever wondered how this magic works and what decisions were made to make this library, this talk is for you. First, we will cover various user scenarios, how the library plays together with them, and what classes do you need to solve your problem. Then, we will dive into low-level interfaces and how the compiler plugin helps us avoid reflection. In the last part, an interesting little example of writing your own serialization format will be presented.