Industrial strength alternative to OCaml's standard library






Portable standard library for OCaml

Core is an industrial-strength alternative to the OCaml standard
library. It was developed by Jane Street, which is the largest
industrial user of OCaml.

Core_kernel is the system-independent part of Core, Jane Street's
industrial-strength alternative to the OCaml standard library. It is
aimed for cases when the full Core is not available, such as in
Javascript. It provides an overlay on the usual namespace, so the best
way to use it is to start your file with:

open Core_kernel

Relationship to Core and Base

In sum:

  • Base: Minimal stdlib replacement. Portable and lightweight and
    intended to be highly stable.

  • Core_kernel: Extension of Base. More fully featured, with more
    code and dependencies, and APIs that evolve more quickly. Portable,
    and works on Javascript.

  • Core: Core_kernel extended with UNIX APIs.

While Core is an extension of Core_kernel, you can think of
Core_kernel as an extension of Base. Many of Core_kernel's modules are
extensions of modules in Base, where the Core_kernel version adds
bin_io support or locks in an API with Stable. Some modules, like
Core_kernel.Map, extend their Base equivalents to follow Core
conventions for the use of comparators.

Please report bugs and feature requests on
GitHub. For everything
else you can contact us at

You can find all of Jane Street's open-source libraries on

Documentation can be found