About Clozure CL

Clozure CL (often called CCL for short) is a free Common Lisp implementation with a long history. Some distinguishing features of the implementation include fast compilation speed, native threads, a precise, generational, compacting garbage collector, and a convenient foreign-function interface.

Clozure CL is distributed under the terms of the Apache License, version 2.0.

Getting Clozure CL

Clozure CL is available for the following platforms:

See the download page to learn how to download and install Clozure CL.


The documentation page has links to pre-formatted versions of the manual.

Documentation for CCL is written in a notation called CCLDoc. Please see the CCLDoc project page for information about this format.


As a free software project, Clozure CL relies on and welcomes contributions and support from its users. For many years, Clozure Associates supported the development of Clozure CL, but CCL is not now, and never has been, a proprietary product.

So, please don't hesitate to partcipate on the mailing list or IRC channel. Keep an eye on the GitHub issues, and if one looks interesting, please let your interest be known!


Mailing lists

The mailing list openmcl-devel@clozure.com is for general and technical discussion of Clozure CL. Note that you must be a subscriber in order to post.


Everyone interested in Clozure CL is welcome to participate in #ccl on libera.chat

Reporting bugs

To report a bug or request a feature, please open an issue on GitHub.