dune is a build system that was designed to simplify the release of Jane Street packages. It reads metadata from "dune" files following a very simple s-expression syntax.

dune is fast, has very low-overhead, and supports parallel builds on all platforms. It has no system dependencies; all you need to build dune or packages using dune is OCaml. You don't need make or bash as long as the packages themselves don't use bash explicitly.

dune supports multi-package development by simply dropping multiple repositories into the same directory.

It also supports multi-context builds, such as building against several opam roots/switches simultaneously. This helps maintaining packages across several versions of OCaml and gives cross-compilation for free.