OCaml Compiler as an esy npm Package

Usage no npm install needed!

<script type="module">
  import ocaml from 'https://cdn.skypack.dev/ocaml';


OCaml packaged for esy

Contributor notes

To package the compiler for esy, a package.json has to be placed in the root with the build instructions.

Getting started

(Request the maintainers to create the target branch beforehand)


  1. Download this patch
  2. Apply the downloaded patch: git apply esy-patch.patch
  3. Test


Requires copying the package.json and the related files from a previous version. (For instance, if you are trying to package 4.11, you can refer 4.10's setup)

These files include

  1. package.json
  2. Git files: .gitattributes and .gitignore
  3. CI files: .ci/ folder and azure-pipelines.yml
  4. Bash scripts: clone-flexdll, configure-windows, esy-build, esy-configure,
  5. Test app: test-app

Verifying the NPM package

  1. Shasum of the published NPM package can be obtained from npm info ocaml
ocaml@4.10.0 | QPL - See LICENSE at https://github.com/ocaml/ocaml | deps: none | versions: 38
OCaml Compiler as an esy npm Package

keywords: ocaml, flow, opam

.tarball: https://registry.npmjs.org/ocaml/-/ocaml-4.10.0.tgz
.shasum: 3797ee252dca8dec38d3cdd42162923f56dba433
.integrity: sha512-HV3V/6VfYli5XTm/DC91YIAbgjB+6vUP/BHrPOHoXi+PAGa83kS4BLV6og3cmYJmrr0RT0hWuIhev+9nSYchHA==
.unpackedSize: 23.8 MB

- foo
- bar

latest: 4.10.0  

published 28 minutes ago by foo <foo@email.com>
  1. shasum of this repo can be obtained by

a) Clone the repo b) Run npm pack inside the repo c) shasum ocaml-<version>.tgz

Note for Windows developers: npm on Windows seems to reset the file perms on the scripts (esy-configure, configure, esy-build). Use a Unix machine or WSL (untested).

Original README


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, MacOS X, MS Windows
IA32 (Pentium)     Linux, FreeBSD, MacOS X, MS Windows
PowerPC            Linux, MacOS X
ARM                Linux

Tier 2 (maintained when possible, with help from users):

AMD64              FreeBSD, OpenBSD
IA32 (Pentium)     NetBSD, OpenBSD, Solaris 9
PowerPC            NetBSD
SPARC              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.


Changes what's new with each release INSTALL instructions for installation LICENSE license and copyright notice Makefile main Makefile README this file README.win32 infos on the MS Windows ports of OCaml asmcomp/ native-code compiler and linker asmrun/ native-code runtime library boot/ bootstrap compiler bytecomp/ bytecode compiler and linker byterun/ bytecode interpreter and runtime system config/ autoconfiguration stuff debugger/ source-level replay debugger driver/ driver code for the compilers emacs/ OCaml editing mode and debugger interface for GNU Emacs lex/ lexer generator maccaml/ the Macintosh GUI ocamldoc/ documentation generator otherlibs/ several external libraries parsing/ syntax analysis stdlib/ standard library tools/ various utilities toplevel/ interactive system typing/ typechecking utils/ utility libraries yacc/ parser generator


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 Institut National de Recherche en Informatique et en Automatique (INRIA) and distributed under the conditions stated in file LICENSE.


See the file INSTALL for installation instructions on Unix, Linux and MacOS X machines. For MS Windows, see README.win32.


The OCaml manual is distributed in HTML, PDF, Postscript, DVI, and Emacs Info files. It is available on the World Wide Web, at



The complete OCaml distribution can be accessed at



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 comp.lang.functional also contains discussions about the ML family of programming languages, including OCaml.


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 caml@inria.fr.