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 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
              
illustration of a cup

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
Facebook
Microsoft
Docker
Jane Street
Bloomberg
Tezos
Ahrefs

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!

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.
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.

VS Code
Vim
Emacs

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

5.1.1 (2023-12-08)

  • Marshall.Compression flag removed from the standard library
  • Bug fixes for 5.1.0

5.1.0 (2023-09-14)

  • Many runtime performance regression and memory-leaks fixes (dynlinking, weak array, weak hash sets, GC with idle domains, GC prefetching)
  • Restored support for native code generation on RISC-V and s390x architectures
  • Restored Cygwin port
  • Reduced installation size (50% reduction)
  • Compressed compilation artefacts (.cmi, .cmt, .cmti, .cmo, .cma files)
  • 19 error message improvements
  • 14 standard library functions made tail-recursive with Tail-Recursion-Modulo-Cons (TRMC), such as List.append and List.map
  • 57 new standard library functions
  • More examples in the standard library documentation
  • 42 bug fixes
See All Releases

Changelog

Releases & Updates

Compiler and Platform Tools

Dune 3.14.0

We're happy to announce that Dune 3.14.0 is now available. This feature has many fixes and new featu...

See full changelog
Ppxlib 0.32.0

The ppxlib dev team is happy to announce the release of ppxlib.0.32.0. The main feature of this re...

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Two months after the release of OCaml 5.1.1, the set of new features for the future version 5.2.0 o...

See full changelog
See Full Changelog

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.

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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.

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OCaml Packages

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

Explore packages