This tutorial covers Circe, a functional JSON handling library for Scala, part of the Typelevel ecosystem and well integrated with Cats. To learn more about Circe: https://github.com/circe/circe To learn more about Monads and Applicative functors: https://www.youtube.com/watch?v=Tx5Ld... To learn more about Type classes: https://typelevel.org/cats/typeclasse... The video covers: 00:00 The overall structure of the library 04:43 The Json data type 13:51 Encoders 17:14 Decoders 30:39 Automatic derivation 32:33 Semi-automatic derivation 34:55 Automatic derivation considered harmful and conclusion A note about the placement of Json codecs and the “automatic derivation considered harmful” part of the video: placing our Encoder[YoutubeVideo] in the companion object of YoutubeVideo would have solved the problem.