http4s servers and clients share an immutable model of
requests and responses. Standard headers are modeled as
semantic types, and entity codecs are done by typeclass.
The pure functional side of Scala is favored to promote
composability and easy reasoning about your code. I/O is
managed through cats-effect.
http4s is built on FS2,
a streaming library that provides for processing and emitting
large payloads in constant space and implementing websockets.