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The developer team released OCaml 5.0.0 in December 2022. This release sports a full rewrite of its runtime system for shared-memory parallel programming using domains and native support for concurrent programming using effect handlers.

Owing to the large number of changes, the initial 5.0 release is more experimental than usual. It is recommended that all users wanting a stable release use the 4.14 release which will continue to be supported and updated while 5.x reaches feature and stability parity. Similarly, if you need one of the ports not yet supported in the 5.0 release you must use the 4.14 release.

The initial release of OCaml 5.0 only supports the native compiler under ARM64 and x86-64 architectures under Linux, macOS and the BSDs. On Windows, only the MinGW-w64 port is supported. Support for other 64-bit architectures and systems will be added back in later releases. On 32-bit systems, only the bytecode compiler will be supported.

Branch trunk Branch 5.1 Branch 5.0 Branch 4.14

Github CI Build Status (trunk branch) Github CI Hygiene Status (trunk branch) AppVeyor Build Status (trunk branch)

Github CI Build Status (5.1 branch) AppVeyor Build Status (5.1 branch)

Github CI Build Status (5.0 branch) AppVeyor Build Status (5.0 branch)

Github CI Build Status (4.14 branch) AppVeyor Build Status (4.14 branch)



OCaml is a functional, statically-typed programming language from the ML family, offering a powerful module system extending that of Standard ML and a feature-rich, class-based object system.

OCaml comprises two compilers. One generates bytecode which is then interpreted by a C program. This compiler runs quickly, generates compact code with moderate memory requirements, and is portable to many 32 or 64 bit platforms. Performance of generated programs is quite good for a bytecoded implementation. This compiler can be used either as a standalone, batch-oriented compiler that produces standalone programs, or as an interactive REPL system.

The other compiler generates high-performance native code for a number of processors. Compilation takes longer and generates bigger code, but the generated programs deliver excellent performance, while retaining the moderate memory requirements of the bytecode compiler. The native-code compiler currently runs on the following platforms:

Tier 1 (actively maintained) Tier 2 (maintained when possible)

x86 64 bits

Linux, macOS, Windows, FreeBSD


ARM 64 bits

Linux, macOS


Power 64 bits


RISC-V 64 bits


IBM Z (s390x)


Other operating systems for the processors above have not been tested, but the compiler may work under other operating systems with little work.

All files marked "Copyright INRIA" in this distribution are Copyright © 1996-2022 Institut National de Recherche en Informatique et en Automatique (INRIA) and distributed under the conditions stated in file LICENSE.


See the file INSTALL.adoc for installation instructions on machines running Unix, Linux, macOS, WSL and Cygwin. For native Microsoft Windows, see README.win32.adoc.


The OCaml manual is distributed in HTML, PDF, and Emacs Info files. It is available at


The complete OCaml distribution can be accessed at

Keeping in Touch with the Caml Community

There is an active and friendly discussion forum at

The OCaml mailing list is the longest-running forum for OCaml users. You can email it at

You can subscribe and access list archives via the Web interface at

An alternative archive of the mailing list is also available at

There also exist other mailing lists, chat channels, and various other forums around the internet for getting in touch with the OCaml and ML family language community. These can be accessed at

In particular, the IRC channel #ocaml on Libera has a long history and welcomes questions.

Bug Reports and User Feedback

Please report bugs using the issue tracker at

To be effective, bug reports should include a complete program (preferably small) that exhibits the unexpected behavior, and the configuration you are using (machine type, etc).

For information on contributing to OCaml, see HACKING.adoc and

Separately maintained components

Some libraries and tools which used to be part of the OCaml distribution are now maintained separately. Please use the issue trackers at their respective new homes: