A composable build system for OCaml
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Dune - A composable build system

Dune is a build system designed for OCaml/Reason projects only. It focuses on providing the user with a consistent experience and takes care of most of the low-level details of OCaml compilation. All you have to do is provide a description of your project and dune will do the rest.

The scheme it implements is inspired from the one used inside Jane Street and adapted to the open source world. It has matured over a long time and is used daily by hundreds of developers, which means that it is highly tested and productive.

Dune comes with a manual. If you want to get started without reading too much, you can look at the quick start guide or watch this introduction video.

The example directory contains examples of projects using dune.

Travis status AppVeyor status


Dune reads project metadata from dune files, which are either static files in a simple S-expression syntax or OCaml scripts. It uses this information to setup build rules, generate configuration files for development tools such as merlin, handle installation, etc...

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

Especially, one can install OCaml on Windows with a binary installer and then use only the Windows Console to build dune and packages using dune.



Take n repositories that use dune, arrange them in any way on the file system and the result is still a single repository that dune knows how to build at once.

This make simultaneous development on multiple packages trivial.

Gracefully handles multi-package repositories

Dune knows how to handle repositories containing several packages. When building via opam, it is able to correctly use libraries that were previously installed even if they are already present in the source tree.

The magic invocation is:

$ dune build --only-packages <package-name> @install

Building against several configurations at once

Dune is able to build a given source code repository against several configurations simultaneously. This helps maintaining packages across several versions of OCaml as you can test them all at once without hassle.

This feature should make cross-compilation easy, see details in the roadmap.

This feature requires opam.

Jenga bridge

Jenga is another build system for OCaml that has more advanced features such as polling or much better editor integration. Jenga is more powerful and more complex and as a result has many more dependencies. It is planned to implement a small bridge between the two so that a dune project can build with Jenga using this bridge.


Dune requires OCaml version 4.02.3 or greater.


The recommended way to install dune is via the opam package manager:

$ opam install dune

You can also build it manually with:

$ make release
$ make install

Note however that make install requires the opam-installer tool. Running simply make will build dune using the development settings.

If you do not have make, you can do the following:

$ ocaml bootstrap.ml
$ ./boot.exe
$ ./_build/default/bin/main_dune.exe install


If you have questions about dune, you can send an email to ocaml-core@googlegroups.com or open a ticket on github.

Migration from jbuilder

Dune was formerly known as jbuilder. Migration from jbuilder to dune is described in the manual.


Dune is now fairly stable and is used by the majority of packages on opam. The package is still in beta version as we are waiting for the renaming from Jbuilder to dune before releasing version 1.0.0. Note that dune will have backward compatibility with Jbuilder, in particular existing Jbuilder projects will continue to be buildable with dune.