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General-Purpose, Industrial-Strength, Expressive, and Safe

OCaml is a general-purpose, industrial-strength programming language
with an emphasis on expressiveness and safety.
Get started About OCaml

                  let square x = x * x
                  val square : int -> int = < fun >
                  square 3
                  - : int = 9
                  let rec fac x =
                  if x <= 1 then 1 else x * fac (x - 1)
                  val fac : int -> int = < fun >
                  fac 5
                  - : int = 120
                  square 120
                  - : int = 14400


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Trusted by Industry Leaders

These companies and organisations rely on OCaml every day -- along
with thousands of other developers. See Success Stories
Facebook
Microsoft
Docker
Jane Street
Bloomberg
Tezos
Ahrefs
BE SAFE

Unobtrusive Type Safety

OCaml's powerful type system means more bugs are caught at compile
time, and large, complex codebases are easier to maintain. This makes
it a good language for running critical code. At the same time,
sophisticated inference makes the type system unobtrusive, creating a
smooth developer experience.
An example OCaml program defining nested lists in OCaml. A terminal
output also shows the compiler catching a type error where a
pattern-match was not exhaustive.
BUILD FASTER

Fast Compiler and Efficient Applications

OCaml has two compilers. One is a bytecode compiler which generates
small, portable executables and is very fast. The other is a native
code compiler that produces more efficient machine code; its
performance matches the highest standards of modern compilers.
[workfaster]
WORK JOYFULLY

First-Class Editor and Tooling

OCaml has great support for the most popular editors. VS Code is
recommended for beginners, and for power users there is deep
integration with Vim and Emacs. OCaml has a rich and dynamic
community and best-in-class tooling. Between Opam, a popular package
manager; Utop, a powerful interactive REPL; and odoc, an easy-to-use
documentation generator, OCaml programmers have access to a complete,
modern developer experience.
[vscode]
[vim]
[emacs]
An OCaml program being edited in VSCode
Writing an OCaml program using emacs
Writing an OCaml program using vim

Vibrant Community

OCaml has a passionate and diverse community, with more than ten
thousand developers and four thousand open source packages. It is a
truly general-purpose language with extensive libraries in a variety
of problem areas, including data science, bioinformatics, and
programming language design. OCaml has roots in academic and
theoretical contexts but has also become popular among application
developers looking to build command-line utilities or performant,
dynamic web apps without resorting to a less safe or feature-rich
language.
 
MirageOS logo
MirageOS
Library operating system to constructs unikernels
 
Js_of_ocaml logo
Js_of_ocaml
Compiler from OCaml to Javascript.
 
Cmdliner logo
Cmdliner
Declarative definition of command line interfaces for OCaml
 
Irmin logo
Irmin
Distributed database that follows the same design principles as Git
 
Dune logo
Dune
A composable build system for OCaml
 
Lwt logo
Lwt
OCaml promises and concurrent IO
 
Owl logo
Owl
OCaml Scientific and Engineering Computing
 
Dream logo
Dream
Tidy Web framework for OCaml and ReasonML

Users of OCaml

OCaml is used by thousands of developers, companies, research labs,
teachers, and more. Learn how it fits your use case.

For Educators

With its mathematical roots, OCaml has always had strong ties to
academia. Currently, it is being taught in universities around the
world, and has accrued an ever-growing body of research. This page
will provide you with an overview of the academic rigor that defines
the culture of OCaml.
Learn more

For Industrial Users

With its powerful compile-time guarantees and high performance,
several companies rely on OCaml to keep their systems operating both
reliably and speedily. On this page, you can get an overview of the
companies in the community and learn more about how they use OCaml.
Learn more

Curated Resources

Get up to speed quickly to enjoy the benefits of the OCaml
programming language across your projects.
 

Getting Started

Install OCaml, set up your favorite text editor and start your first
project.

 

Language Manual

Read the reference manual of the language and documentation on the
compiler.

 

Books

What expert programmers and researchers are saying about OCaml, from
the beginner level to more advanced topics.

 

Standard Library

Searchable API documentation.

 

Exercises

Learn OCaml by solving problems on a variety of topics, from easy to
challenging.

 

Papers

Papers that have influenced OCaml and other functional programming
languages.

OCaml Packages

Explore thousands of open-source OCaml packages with their
documentation.

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