Why Core?

A standard library, with batteries included

Core is a souped-up and filled-out version of Base, Jane Street’s minimal standard library replacement. Some Core modules are extensions of their counterparts in Base, usually adding generic functionality by including functors that make them binable , comparable , sexpable , blitable , etc.

The APIs in Core are more full-featured, but do move faster than those in Base.

Getting started


$ opam install core


open Core

API Documentation

See here for complete API docs.

Where Core fits in

Jane Street has three standard library packages that offer varying levels of completeness and stability. Here’s how they fit together:


Minimal stdlib replacement. Portable and lightweight and intended to be highly stable. See the page for Base.


Portable component of Core, working on Javascript and Windows. Core_kernel’s API Docs


Fully-featured extension of Base.