OCaml is an implementation of the ML language, based on the Caml Light dialect extended with a complete class-based object system and a powerful module system in the style of Standard ML.
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 essentially any 32 or 64 bit Unix platform. 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, toplevel-based 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 used and maintained by the core OCaml team):
- AMD64 (Opteron)
Linux, OS X, MS Windows
- IA32 (Pentium)
Linux, FreeBSD, OS X, MS Windows
Linux, OS X
Tier 2 (maintained when possible, with help from users):
FreeBSD, OpenBSD, NetBSD
- IA32 (Pentium)
NetBSD, OpenBSD, Solaris 9
Solaris, Linux, NetBSD
Other operating systems for the processors above have not been tested, but the compiler may work under other operating systems with little work.
Before the introduction of objects, OCaml was known as Caml Special Light. OCaml is almost upwards compatible with Caml Special Light, except for a few additional reserved keywords that have forced some renaming of standard library functions.
what’s new with each release
how to contribute to OCaml
instructions for installation
license and copyright notice
MS Windows Makefile
used by manual/ and testsuite/ Makefiles
info on the MS Windows ports of OCaml
native-code compiler and linker
native-code runtime library
bytecode compiler and linker
bytecode interpreter and runtime system
the OCaml compiler as a library
source-level replay debugger
driver code for the compilers
editing mode and debugger interface for GNU Emacs
experiments not built by default
empty (see README.win32.adoc)
system to generate the manual
the flambda optimisation phase
several external libraries
All files marked "Copyright INRIA" in this distribution are copyright 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016 Institut National de Recherche en Informatique et en Automatique (INRIA) and distributed under the conditions stated in file LICENSE.
The complete OCaml distribution can be accessed at
Keeping in Touch with the Caml Community
There exists a mailing list of users of the OCaml implementations developed at INRIA. The purpose of this list is to share experience, exchange ideas (and even code), and report on applications of the OCaml language. Messages can be written in English or in French. The list has more than 1000 subscribers.
Messages to the list should be sent to:
You can subscribe to this list via the Web interface at
Archives of the list are available on the Web site above.
The Usenet news
groups comp.lang.ml and
contains discussions about the ML family of programming languages, including
The IRC channel
#ocaml on Freenode also has several
hundred users and welcomes questions.
The OCaml Community website is
Bug Reports and User Feedback
Please report bugs using the Web interface to the bug-tracking system at http://caml.inria.fr/bin/caml-bugs
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).
You can also contact the implementors directly at firstname.lastname@example.org.
For information on contributing to OCaml, see the file CONTRIBUTING.md.