GeezerVison is showing ocaml.org — Welcome to a World of OCaml
OCaml
An industrial-strength functional programming language
with an emphasis on expressiveness and safety
# let square x = x * x
val square : int -> int = < fun >
# square 3
- : int = 9
# let rec factorial x =
if x <= 1 then 1 else x * factorial (x - 1)
val factorial : int -> int = < fun >
# factorial 5
- : int = 120
# square 120
- : int = 14400
The OCaml Compiler has been recognised by SIGPLAN for their prestigious Programming Languages Software Award
Fourteen core OCaml developers are featured for their
significant contributions to the project
Trusted by Industry Leaders
These companies and organisations rely on OCaml every day — along with thousands of other developers. See Success Stories
Why OCaml?
RELIABILITY
Powerful Type Safety Made Simple
OCaml’s lightweight but highly expressive type system catches more bugs at compile time while garbage collection allows you to focus on application logic instead of memory management.
Large, complex codebases become easy to maintain and refactor.
OCaml empowers you to create mission-critical software with
highest security- and safety-requirements in environments with
ever-changing requirements!
PRODUCTIVITY
First-Class Editor and Tooling
OCaml comes with deep integrations for VS Code, Vim or Emacs to provide type inspection, autocomplete and more.
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.
PERFORMANCE
Fast Compiler and Applications
OCaml offers great runtime performance without compromising on developer experience:
The bytecode compiler generates small, highly portable executables blazingly fast;
the native code compiler produces highly-efficient machine code. Despite this focus
on performance, the OCaml compiler has always been exceptionally reliable and stable
Exceptionally Robust and Reliable
Despite all this testing, we have never had a single XenServer defect reported from
internal testing or from the field that can be traced back to a bug in the
OCaml runtime or compiler. (During development we did once find a minor compiler bug,
triggered when compiling auto-generated OCaml code with many function arguments,
but this was already fixed in the development branch by the time we reported it
and so no interaction with the maintainers at INRIA was required.)
-- Scott, D. & Sharp, R. & Gazagnaire, T. & Madhavapeddy, A. (2010).
Using Functional Programming within an Industrial Product Group: Perspectives and Perceptions.
ACM SIGPLAN Notices. 45. 87-92. 10.1145/1863543.1863557.
Releases
Recent Releases
5.5.2 (2026-10-23)
- Bug fixes for 5.5.1
- Various Security Fixes: OSEC-2026-21, OSEC-2026-22, OSEC-2026-23, OSEC-2026-24,
OSEC-2026-25, OSEC-2026-26
See All Releases
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.
It is taught in universities around the world, and has accrued an ever-growing body of research.
Learn more about the academic rigor that defines the culture of OCaml.
Learn more
For Industrial Users
OCaml's powerful compile-time guarantees and high performance empower
companies to provide reliable and speedy services and products.
Learn more about how OCaml is used in the industry: explore success stories and discover companies that use OCaml.
Learn more
Curated Resources
Get up to speed quickly to enjoy the benefits of the OCaml programming language across your projects.
OCaml Packages
Explore thousands of open-source OCaml packages with their
documentation.
Explore packages
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